Widowmaker:  Genji is one of the best counters to a Widowmaker.  Genji's Parkour abilities allow him to sneak around the map and get closer to the Widowmaker to kill her.  Genji can use Deflect to prevent a Widowmaker from even trying to shoot him while he approaches her.  If a Widowmaker hits a Genji's Deflect, she will take upwards to 120 damage from her 200HP pool.  Widowmaker can make it harder for Genji to Deflect her shots by strafing around to avoid the deflections.

Watch out for Widowmaker's Venom Mines as she will usually place them in areas to hurt offensive flankers such as Genji.  You can destroy the mines by shooting at them.  You CANNOT Swift Strike past a Venom Mine to avoid it, as it will still trigger.

Once you get close to her, simply use Genji's deadly combo to quickly take her out.

Widowmaker's ultimate Infra-Sight is very useful for tracking down if a Genji is getting closer to flank her.  If she sees you approaching, she can quickly grappling to somewhere safer.  When Widowmaker uses Infra-Sight, you should highly consider focus on killing other heroes until it wears off.

Bastion:  From long range, Shurikens do well at damaging a Bastion Sentry, since aiming at stationary targets are very easy with shurikens.  If Bastion spots you, just move somewhere else and keep attacking.

All of Genji's abilities will help you to get behind a Bastion to flank him.  You can use wall climb, Swift Strike and Deflect to get closer to a Bastion Sentry.  A properly executed Swift Strike can be devastating to a Bastion Sentry, as it will be hard for Bastion to find out where you are exactly after swift striking.  Bastion will need to turn around and start firing at you, which would also be a good time to use a Deflect against him.  At this point you can then turn on Dragonblade if you need to kill anyone else in the area.

Thanks to Genji's wall climb and Swift Strikes, he is also a good counter for an elevated Bastion due to Mei's Ice Wall boost.

I want to stress again how important Deflect is against a Bastion Sentry.  You can easily kill Bastion Sentries by using Deflect on his bullets to return it right back to him to quickly take him out in a small fraction of a second usually, very effective strategy.

Deflect also works great against Bastion's ultimate Tank Form.  Simply use Deflect on one of his cannon balls, aim it right back it him to deal 190 damage to his 300 HP pool.

Ana:  Dealing with Ana is not too bad.  Just try to make yourself a hard target to hit to avoid her Sleep Darts and Biotic Grenades.  Deflect works very well against all of Ana's normal abilities.  You can Deflect her Sleep Dart to potentially put her or one of her teammates to sleep instead.  You can also Deflect her Biotic Grenade to deal damage to Ana and her team while also prevent healing done to them as well.

Landing a Sleep Dart on Genji is going to be difficult for Ana, Genji's Deflect along with his Swift Strike and double jumps will make it extremely hard for Ana to land Sleep Darts.  If Ana does manage to put Genji to sleep it will also make your cooldowns for Swift Strike and Deflect wind down making you more powerful once you awaken.

If you Swift Strike up to Ana, her best bet is to try to throw everything she has at you.  Ana will most likely first try a Sleep Dart, if that misses she will try to use a Biotic Grenade to potentially do some damage to you while healing her up a bit.  If you use Dragonblade she will try to use the same tactics as well.  Ana may try to Nano Boost one of her allies to help fend off the Dragonblade.

Mercy:  Mercy is the heart of the enemies army and she is usually hiding out of the line of the enemy's sight.  Genji can parkour around the map in places where the enemy may not expect it, allowing you to kill her quickly.

Hanzo:  Brother Vs brother, who wins?  I think overall it's a close matchup, but Genji might have the upper hand with his Deflect ability.  Genji would need to time Deflect very precisely though which can be a bit difficult.  Genji can Delfect Hanzo's Sonic Arrow and Scatter Arrows making them a Sonic Arrow or Scatter Arrow for Genji's team.  Genji can also Deflect the initial arrow from Hanzo's ultimate Dragonstrike, sending it back at Hanzo and turning it into a Dragonstrike for Genji's team.  But Genji cannot Deflect the actual Dragon once deployed.

Although one good shot of Hanzo's scatter arrows and it's GG for Hanzo.  As Genji, you can kind of avoid Scatter Arrows by continuously double jumping when around Hanzo, as it will make it harder for him to aim Scatter Arrows at the ground in front of you.

Genji's ultimate Dragonblade seems to be more useful than Hanzo's ultimate Dragonstrike when fighting 1vs1.

Pharah:  Pharah is usually out of Genji's reach with her jetpack ability.  Genji generally has a hard time aiming shurikens at the flying Pharah.  Deflecting Pharah's rockets can be difficult since she is always moving in the air and will easily avoid the deflections.  Genji can attempt to swift strike her as she gets lower to the ground to deal some damage however.

Genji can avoid Pharah's ultimate Barrage with a Deflect along with running behind a wall to avoid the rest of it.  Unfortunately, Pharah can avoid Genji's Dragonblade by simply launching into the air to avoid it.

Symmetra:  Genji is the type of hero that wanders around the map trying to pick off stray enemies.  Because of this, Symmetra's Sentry Turret traps can be especially lethal to Genji.  Symmetra can put her traps in rooms or hallways around the map to deal a lot of damage to a wandering Genji.  Genji also has a harder time hitting the sentry turrets with his shurikens (as opposed to other heroes).  Remember you can always use a Swift Strike to escape out of rooms with deadly turret nests if you need to.

Symmetra's short range beam weapon works great against a Genji since you cannot deflect it.  However you can deflect Symmetra's deadly photon orbs.

Genji's roles and abilities enables him to do a decent job at finding and taking out Symmetra's Teleporter (ultimate) as long as you can make it past her turret nests.

Dragonblade happens to be very deadly against Symmetra as long as you can make it up close to her.  She has poor mobility and won't be able to escape it.

Mei:  Genji is relatively weak against Mei because she can use her freeze gun on Genji and it cannot be deflected.  Although Genji can use a Swift Strike to escape out of the way to prevent getting frozen.  Mei can use her Icewall to avoid Genji's attacks and Cryo-Freeze herself after Genji Swift Strikes her.  Even though Genji can jump/climb over her icewall, the icewall still slows a Genji down quite a bit, thus giving Mei enough time to escape.  If Genji uses his ultimate Dragonblade, Mei can simply use Cryo-Freeze to protect herself from it.  1vs1, Genji is better off staying a distance from Mei and using Shrukens to deal damage.

Remember that Genji can use a Deflect on Mei's Blizzard drone to send it back towards Mei to act as a Blizzard for Genji's team.

Tracer:  Fighting a Tracer as Genji can be quite annoying.  It can be difficult to throw shurikens or swift strikes at a Tracer since she moves around so fast.

Tracer's Pulse Bomb / Recall combo can be deadly to Genji.  Normally you can Swift Strike away from a Pulse Bomb, but if Tracer is able to throw the bomb on Genji so it sticks, there is nothing Genji can do to escape it.  Genji can use Deflect on Pulse Bombs to repel them away from him.

Tracer can avoid Dragonblade by simply blinking away from it.

Zarya:  Zarya's powerful Particle Cannon Beam cannot be deflected, but her alternate fire (charged shots) can be deflected.  Zarya's barriers only make it harder to damage her.  As Genji, you are better off keeping a distance from Zarya and throw shurikens at her, you can then get close to her once she gets low on health.

If you happen to get caught in Zarya's ultimate (Graviton Surge) you can simply escape out of it with a Swift Strike.  Also keep in mind, Genji can actually Deflect the initial black projectile of Graviton Surge, which will cause a Graviton Surge for Genji's team instead.

Dragonblade happens to be deadly against Zarya as her poor mobility makes it so she cannot run away from you while it's active.  You will just need to watch out for her using a Particle Barrier.  I would only use Dragonblade against her once her Particle Barrier runs out.

Lucio:  Lucio is hard to hit with shurikens because of how fast he moves around with his skates, especially when he has his speed aura on.  Plus the fact that Lucio can provide increase movement for his whole team can make throwing shurikens at every enemy extremely difficult.  Lucio can also heal up Shuriken damage with his heal aura.

Even though Lucio's sonic projectiles can be deflected, it's not very effective against Lucio because of how slow the projectiles move and how fast Lucio can move to avoid it.

Swift Strikes can be effective against Lucio, you just need to watch out for getting knocked back with Lucio's Soundwave, which is not much of a problem for Swift Strike.

Lucio and his team can easily avoid Genji's Dragonblade with a quick drop the beat (Lucio's Sound Barrier ultimate).  If his Sound Barrier is not available to him, he can use his speed aura with Amp It Up to allow him and his team to run away from it quickly.  Lucio can also use Soundwave to knock back Dragonblade.

Winston:  Winston's weapon cannot be deflected and his globe shields provide him protection against Genji's shurikens.  Genji's swift strikes are weak due to Winston's massive hitpoints and automatic aiming with his Tesla Cannon.  It's hard to run away from a Winston since he can just leap at you.

Your best bet against Winston is to use your Dragonblade ultimate on him, as it will deal more DPS than he can do back to you.

D.va:  Tanks are hard for Genji to deal with but with D.va it's a bit easier than a Winston.  The main problem with D.va is her boosting ability.  Running away from a D.va is difficult due to D.va's fast flying ability.  Her Boosters also enable her to run away from Genji saving herself from Swift Strikes and Dragonblade.

Deflect is also less effective on D.va because she can easily let go of the trigger to stop her stream of bullets when deflect gets turned on, this ensures much less bullets will get deflected dealing less reflected damage.

As Genji, you are better off keeping your distance from D.va while throwing Shurikens at her, up close her Fusion Cannons are too powerful, and combined with her Boosters makes her a deadly hero to go up against for Genji.

Torbjorn:  Even though Genji has great mobility and can get up close to Torbjorn's turret, he can still have a rough time with Torbjorn and his turret due to the massive amount of damage and fire power he will have to deal with.

Genji does have some methods of dealing with Torbjorn's turret.  A Turret will still attack Genji if he uses deflect, and the deflected bullets can take out the turret as well.  Genji can also throw shurikens at the turret from a distance to do some decent damage to it.  Genji's Swift Strike does NOT reset the cooldown if he eliminates a turret with Swift Strike.

Genji can go all out with Swift Strikes and Shurikens, but in the end it can be a tough fight for Genji.  If Genji uses his ultimate Dragonblade it can be countered with Torbjorn's Molten Core.

McCree:  A good McCree player can be devastating to Genji.  Most new McCree players will try to throw their Flashbangs directly at Genji.  The issue with this is that Genji can Deflect Flashbangs thrown right at him.  But McCree can actually throw a Flashbang either into the ground in front of Genji or up in the air above Genji to avoid his Deflects and successfully get the Flashbang stun in.

McCree is extremely deadly 1vs1 for just about every hero in Overwatch.  As Genji, be very cautious when facing a McCree, consider backing away from him to avoid his Flashbangs or quickly do a Swift Strike combo at him immediately when you make contact with him.  Keep your distance from him if you can and remember McCree has poor vertical mobility, so getting up high can be effective against him.

When McCree uses his ultimate Deadeye, Genji can use Deflect against it to easily take him out if he fires at you.  If Deflect is not ready, then try to Swift Strike out of his line of sight quickly.

Reaper:  Going up against a Reaper is somewhat of a fair fight.  Both heroes have ways to escape out of combat.  As Genji, you will want to try to stay a distance from Reaper, as his shotguns are very deadly up close.  You can use Genji's climb ability to help you achieve that.

Genji's Deflect works great against Reaper.  If Reaper fires at you with Deflect on, you will be able to instantly transfer the damage right back to him, thanks to the instant hitscan nature of Reaper's shotguns.  This makes using Reaper's ultimate Deathblossom around Genji devastating to Reaper.  If you see a Reaper using Deathblossom, you can Swift Strike right up to him and then activate Deflect and it will usually kill Reaper very fast.

Be careful using Dragonblade around Reaper as Genji is still very vulnerable to Reaper's deadly shotguns.  Remember you can still use Deflect while Dragonblade is active and this would be an important time to use it while using Dragonblade.

Soldier 76:  Like Reaper, getting close to a Soldier 76 can be deadly as his weapon is strong and he can heal himself along with his allies with Biotic Fields he can put down.

Deflect is very effective against Soldier 76, especially when he uses his ultimate Tactical Visor.  Deflect has a chance to take him out if enough bullets get repelled back at him.

Roadhog:  Even though all tanks give Genji a hard time, Roadhog is one of the easier tanks to deal with.  Genji can deflect Roadhog's shotgun and Chain Hook attempts, but you still have to watch out for getting chained in.  Stay a distance while strafing around and lobbing shurikens at Roadhog's head and you'll be fine.

If you get chained in, immediately use Deflect to block any shots right back at Roadhog while backing up to escape.  You can also Swift Strike through Roadhog to get away from him, but be careful where you will Swift Strike to, you may be better off just using Deflect and Swift Striking back to safety.

Dragonblade happens to be somewhat effective against Roadhog.  It will take 5 swipes from Dragonblade to take out a Roadhog from full HP.  Roadhog's Chain Hook will NOT cancel Dragonblade.  Although, Roadhog can use his ultimate Whole Hog to knock you away from him and his team while Dragonblade is active.

Zenyatta:  Zenyatta should be a prime target for you to flank as he is a strong but squishy support hero with poor mobility.  Zenyatta's Discord Orb is what makes going 1on1 with him somewhat difficult.  Discord Orb is very deadly to anyone who has it and when put on Genji it will make things a lot tougher for you.  Deflect will not prevent Zenyatta from throwing the Discord Orb on you, but Deflect can be used to block additional damage while the Discord Orb is on you.  You can also use a Swift Strike to quickly get behind a wall to remove it.  If you are out in the open, then try your best to focus fire on Zenyatta and kill him first.

All of Genji's attacks work great against Zenyatta and taking him out shouldn't be to much of a hassle for you.  Watch out if Zenyatta uses his ultimate Transcendence, you are usually better off staying away from in until it is over.

Reinhardt:  Genji has great mobility and is able to get high up and away from Reinhardt and most of his abilities, from there he can pick at Reinhardt with his shurikens.  Reinhardt can block shurikens with with his shield most of the time, however Genji may be able to get all the way behind his team and harass Reinhardt from behind, which can be difficult to counter as Reinhardt as he will depend on his team to take out the wandering Genji as there is not much he can do about it except fling a Fire Strike at Genji, which can also be repelled by Deflect.

Up close battles are dangerous between both of the heroes, Swift Strikes can do an ample amount of damage (even through shields) and Genji can then use Dragonblade up close, but Reinhardt can counter that with an Earthshatter followed by a Charge or Fire Strike.  Keep in mind that Deflect will block Reinhardt's deadly melee attacks.

A double jump in the air can sometimes avoid Reinhardt's Earth Shatter ultimate (but not always), so keep jumping when you get near to him to avoid sudden Earth Shatters.

Genji's Dragonblade can be used through Reinhardt's shield, making it a bit more useful against him.  A Dragonblade can deal damage to both Reinhardt and his shield with one swipe.

Junkrat:  Close match up.  Junkrat will try to stay around walls/corners while lobbing grenades and hiding traps/mines for the approaching Genji.  Genji can deflect Junkrat's frag grenades and Concussive Mines, but not his Traps.

Both heroes have good mobility, Junkrat can Mine jump away from Genji's Dragonblade and Genji can Swift Strike or climb away from Junkrat's ultimate Rip-Tire.

Keep in mind that Swift Strike does not damage Junkrat's mines and traps, in fact Junkrat's Steel Trap will still trap a swift striking Genji.

Be careful when killing Junkrat up close, as his Total Mayhem death bombs can do a lot of damage.  Genji can actually Deflect these bombs if you catch it in time.

Genji:  When dealing with another Genji it generally comes down to who can pull of their combos faster than the other Genji.  Remember that Deflect has no use against Swift Strike or Dragonblade.  When another Genji approaches you with Dragonblade, it is usually best to Swift Strike away from it.