Ana:  Due to Ana's poor mobility, she tends to be weak against offensive flankers like Tracer.  Tracer's fast Blinks and small hitbox will make it very difficult for Ana to land Biotic Rifle shots at her along with Sleep Darts as well.  This makes Tracer one of the best flankers against Ana.  Even if Ana does land a Sleep Dart on Tracer, it will allow all of Tracer's Blinks and Recall to replenish while sleeping which will allow her to escape or reposition somewhere else very fast once she awakens.

Ana's best bet against Tracer is to throw a well aimed Biotic Grenade at Tracer to do some damage, as the splash radius will make it easier to land a shot at her.  Ana should try to stick with her allies more so they have her back.  Ana can Nano Boost an ally near her to help scare Tracer away from her.

Ana's poor mobility makes her very susceptible to Tracer's Pulse Bomb, and there is not much Ana will be able to do about that.

Bastion:  Bastion's biggest counters are the offensive heroes, especially the ones that are able to move around the map quickly and unnoticed.  Tracer excels in this area very well, she can Blink around very fast to get around Bastion to flank him.  Her abilities allow her to zip right to a Bastion and throw a Pulse Bomb, and then Recall out of there to save her.  Very powerful and there isn't a whole lot Bastion can do about it.

Remember that hitting a Bastion Sentry in the rear will do double the damage to him.  Running right past Bastion can really confuse him on which way to turn to fire at you, this can give you an easy time to take him out with your Pulse Pistols.

Mercy:  With Tracer's ability to get virtually anywhere on a map (even in deadly situations), comes in handy especially for killing Mercys.  A Lot of times Mercy is hiding behind walls or pillars to avoid enemy fire, but Tracer is able to zip around these areas to kill Mercy very effectively.  Like Bastions, Pulse bombs are recommended if Mercy is heavily guarded and you need to get in and out real quickly.  Mercy has no counters for a stuck Pulse Bomb.

Widowmaker:  Fast moving targets are very annoying for Widowmaker, thus Tracers are very hard to hit for her, even in long ranges.  Like Bastions and Mercy, Widowmaker is another prime target for Tracer to take out.  Strategies are similar to Bastion and Mercy, except Widowmaker can put down what I call flanker traps (Venom Mine), which can be devastating to Tracers.  Venom Mines can stick to walls or ceilings and do poison damage over time and knock out 75 HP from you if Recall is not used fast enough once triggered.  Widowmakers tend to put these mines in choke points leading up to her sniping spot, so watch out for her Venom Mines when getting closer to her.  Keep in mind that Tracer can Blink past a Venom Mine unharmed.

Even though Widowmaker has no counters to remove a stuck Pulse Bomb, Tracer can usually just kill her with Pulse Pistol damage.

Torbjorn:  Many heroes can damage Torbjorn's turret from long distances, but in a lot of instances Torbjorn is behind the turret in a safe spot repairing it, making it incredibly difficult to get around there to stop him.  Luckily Tracer is one of the few heroes that has the ability to get around safely via blinking and take Torbjorn out and maybe his turret too.  It's usually only advisable to do so only when combined with a Pulse Bomb, because it doesn't take long for a turret to take out Tracer.

Keep in mind if Torbjorn has a level 3 turret, it will take more than a Pulse bomb to kill it.  Pulse Bombs only do 400 damage.  A level 1 turret has 150 HP, level 2 has 300 HP, and level 3 has 800 HP.  So if it's a level 3 turret you will also need to deal some damage with your Pulse Rifle in order to take it out.  Because of this, I find it's more advisable to use your Pulse Bomb on Torbjorn himself and deal with the turret later once it reverts back to level 2 once his Molten Core runs out.

Reinhardt:  Tracer is one of Reinhardt's worst nightmares, and this is thanks to her powerful blink, pulse bomb, and recall combo.  Reinhardt's shield is very beefy and takes a lot of fire power to take down, and even then the shield recharges fast when not in use.  One needs to get to the source of the problem.  Tracer is able to deal with the source via Pulse Bombing Reinhardt himself, which can result in a kill for Tracer.  However, Pulse Bombs do 400 damage so it may not be enough to take out a Reinhardt at full HP (of 500).

Since Tracer moves around so fast, there is not a whole lot Reinhardt can do about this.  When doing this strategy it's usually best to actually make sure you use Recall or blink quickly because staying next to Reinhardt for too long can be devastating to Tracer as he can use his Rocket Hammer or Earthshatter, followed by a Charge to take her out.  Also, Reinhardt's shield will block Pulse Bombs from hurting him and his team behind the shield.

Tracer can actually Blink past a Charging Reinhardt, to prevent getting pinned by his Charge.

Genji:  Since Tracer moves around so fast, it is very difficult for Genji to land his shurikens or Swift Strikes at her.  The Pulse Bomb / Recall combo can be deadly to Genji.  Normally he 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.

If Genji uses his ultimate Dragonblade, Tracer can avoid it by simply blinking away from it.

Zenyatta:  Zenyatta can be very deadly in 1on1 situations thanks to his Discord Orb and Orb of Destruction weapon, which uses fast flying projectiles that are actually pretty powerful, but Tracer is the hardest hero to hit with his orbs.  Tracer can use Recall to remove Zenyatta's Discord Orb, and this is why I have her listed as stronger than Zenyatta.  Tracer can also use Blinks to quickly get behind a wall to remove the Discord Orb.  So always remember this!

Zenyatta can save himself from Tracer's Pulse Bomb with his ultimate Transcendence, but it won't necessarily save his teammates from a Pulse Bomb, since it does 400 damage on contact.

Hanzo:  Tracer is a tough fight for Hanzo, as it is incredibly difficult for Hanzo to hit fast & small moving objects with his Storm Bow.  One would need to be really good with Hanzo (lots and lots of practice) to get better at shooting down Tracers.

Hanzo can shoot a Sonic Arrow on Tracer and it will follow her, allowing Hanzo's team to see exactly where she is at.   ButTracer can dispel the Sonic arrow from her by using Recall.  The dispelled Sonic Arrow will drop to the ground and continue to provide infra vision for Hanzo's team for its remaining duration.

Tracer can easily avoid Hanzo's ultimate (Dragonstrike) by blinking away from it, but Hanzo will most likely die to Tracer's Pulse Bomb, as there is not much Hanzo can do about it.  However, I predict when it comes down to high level of play, this will become more of an even fight between the two.

Mei:  Mei can be tough to deal with as Tracer.  Mei's Icewall can trap a Tracer close to Mei, making it harder for Tracer to use blink to escape, this allows Mei to then freeze Tracer with her freeze gun.  Tracer would need to use Recall in this situation in order to easily escape that.  If you managed to get some damage off on Mei, that wont matter a whole lot since Mei can just freeze herself to regain her health back.

In close to mid range Mei can one shot Tracer to death with one Icicle shot to the head unless Tracer has either an armor pack on, Photon shield, or Sound Barrier.

The Pulse Bomb / Recall combo is not very effective on Mei, since she can just use Cryo-Freeze real quick to save her.  On the bright side, if Mei uses her ultimate (Blizzard), Tracer can just blink away from it to avoid it.  You can also Blink away while Mei has her freeze gun on you to quickly escape out of it.

Soldier 76:  Soldier 76 is a good overall counter for Tracer.  His Pulse Rifle works well in all ranges, and if Tracer gets too close to Solder 76, he can potentially shoot a Helix Rocket at her.  As Tracer, if you get too close to Soldier 76, keep jumping, that will help you avoid further damage from Helix Rockets since most will be fired at the ground near Tracer.  A lot of times it can be hard to kill a Soldier 76, since he can just heal himself after taking some damage from Tracer.  The Pulse Bomb and Recall combo is really the best way to deal with a Soldier 76, as there is not much he can do about it.

Junkrat:  Fast moving ground targets are an easy prey for Junkrat's traps because it's very hard to spot them before you hit them.  Tracer's fast movement makes it difficult to dodge Junkrat's traps and this is the main reason why Junkrat is stronger than Tracer overall.  Although, Tracer can actually Blink past a Trap unharmed.

Dodging Junkrat's Frag Launcher can be quite difficult due to the randomness of the grenades bouncing around, this can make it difficult to get close to Junkrat.  Also if you happen to get stuck in one of Junkrat's Steel Traps, it is usually a good bet to use Recall at that second to avoid being blown away by a Concussion Mine before Junkrat Triggers it.  NOTE:  Junkrat usually place their mines right next to a Steel Trap and trigger the mine to go off once the trap gets triggered.

If you hear "Fire in the Hole" during a game, this means that an enemy Junkrat just initiated his ultimate (Rip-Tire), in order to avoid this simply blink away from it.

Pharah:  Tracer has very poor vertical mobility, so it's usually very difficult for Tracer to reach close to flying objects.  This is the reason why Pharah has the advantage over Tracer.  Tracers can be hard to hit thanks to her blink ability, but it only takes a few good rocket shots from Pharah to kill her.  When Pharah lands on the ground from a Jump Jet, Tracer can do some good damage to Pharah with her Pulse Pistols.  Pharah can use a Concussive Blast to propel herself away from Tracer until she can use Jump Jet again.

Pharah can usually avoid Tracer's ultimate (Pulse Bomb) thanks to her flying ability, but if Tracer manages to stick a Pulse Bomb on her, there is nothing Pharah can do to counter it.

Tracer can usually just blink away from Pharah's ultimate (Barrage).

Reaper:  Reaper's shotguns simply do more damage than Tracer's Pulse Pistols.  A Reaper with good aim is very devastating to Tracer, and he will usually come out on top.  Both heroes have ways of avoiding each other's ultimates.  Reaper can use Wraith Form to avoid Tracer's Pulse Bomb, and Tracer can use blink to avoid Reaper's ultimate (Death Blossom).  As Tracer, I would avoid facing a Reaper during high level of play, but I would say most of the time a Reaper Vs Tracer fight is about even.

Roadhog:  Roadhog and Tracer both have a hard time killing each other.  Roadhog has a lot of hitpoints, and it will take a long time for Tracer to put a dent in him.  Tracer's recall is a great counter to Roadhog's Chain Hook.  If Roadhog uses chain hook on Tracer, she can then use Recall to fully escape out of it.  As Tracer, I would not go near a Roadhog if your recall or multiple blinks are not ready, as it only takes a few close up shots to kill a Tracer.

Roadhog can serve as a way to charge up your ultimate faster, as he is a big target with a lot of hitpoints, but you still need to be careful around him as he can kill you quickly with his deadly Chain Hook combo.

Roadhog is one of the few heroes in the game that can survive a direct Pulse Bomb explosion.  Pulse Bombs do 400 damage and Roadhog has 600 total HP.  Pulse Bombs do not have any stun effects, so it will NOT cancel out Roadhog's Take a Breather (self-heal) or Whole Hog ultimate.

If Roadhog uses his ultimate Whole Hog, simply blink away from it to avoid it.

Overall, Roadhog is typically not a prime Target for Tracer.  She is better off dealing with other heroes and keeping her distance from Roadhog.

Winston:  Like Symmetra's weapon, Winston's Tesla Cannon works very well on Tracer thanks to the automatic aiming, as it does okay at damaging Tracer even while blinking as long as she is in range of him.  As Tracer you generally don't want to be around Winston for too long because of his Tesla Cannon and his high HP of 500, as he would take awhile to take down with your Pulse Pistols.  Instead, focus on weaker heroes to harass and pick off.

Tracer's Pulse Bomb is a good counter to Winston's Barrier Projector.  Tracer can blink into the Barrier real quick, lob a Pulse Bomb, then Recall out of there, dealing massive damage for anyone taking cover under the Barrier.

If Winston uses his ultimate (Primal Rage), Tracer can simply blink away from it.

McCree:  McCree is overall very deadly in close range with just about any hero, except Tracer will give him a tough time due to her fast mobility.  If McCree successfully lands his Flashbang on her, Tracer will pretty much die.  Keep in mind Tracer is most vulnerable to getting Flashbanged when she is firing her guns at McCree, so you need to have very fast reflexes during this time to quickly avoid the Flashbangs.  Tracer can usually avoid McCree's ultimate (Deadeye), as long as she can figure out where McCree is standing, and then simply blink away to take cover from it.  Tracer's Pulse Bomb and Recall combo is very deadly to McCree, and there is not much he can do about it.

Lucio:  Dealing with a Lucio as Tracer can be annoyingly difficult.  Lucio can use his alternate fire Soundwave to knock back Tracer if she gets close and his healing aura can quickly restore the damage done by her Pulse Pistols.  And worst of all, Lucio is the best counter to Tracer's Pulse Bomb with his ultimate (Sound Barrier), protecting all his teammates in the area who got bombed.  It's generally a better idea for Tracer to use her Pulse Bomb shortly after Lucio uses Sound Barrier so it doesn't get blocked.

However, Lucio will have a hard time killing Tracer since she moves around so fast and it can be difficult for Lucio to aim his Sonic projectiles at her.  Overall the fight is somewhat even and they will both have troubles taking each other out.

Symmetra:  Like Winston's short range Telsa Cannon, Symmetra's short range Photon Projector beam actually works well on Tracer because of how it automatically aims at her (even while blinking).  Because of Symmetra's weapon, it's probably a good idea to keep somewhat of a distance from her.

Because Tracer moves through hallways and passages to get around the enemy to flank them, Symmetra usually places her Sentry Turrets in these areas to take out heroes like Tracer.  So you need to be extra cautious if you know the enemy has a Symmetra on their team and be prepared to either quickly Blink past them or take out her turrets if you see them.  Tracer's weapon is decent at taking out sentry turrets, but she only has 150 hitpoints, so it wont take long for her to die to the turrets.  You can also use a Pulse Bomb to clear out a room filled with sentry turrets if you really need to.

Symmetra's Teleporter is a prime target for Tracer, and it is her job (along with other offensive heroes like Genji and Reaper) to take out her Teleporter.

Tracer's Pulse Bomb can be deadly to Symmetra, as there is nothing Symmetra can do to counter a stuck Pulse bomb.

Zarya:  Zarya's Particle Cannon weapon is actually decent against Tracer and since Zarya is able to take a lot of damage, she will be hard for Tracer to take down.  Zarya is one of the harder heroes to flank due to her Particle Barrier, which makes her invulnerable for a few seconds and any damage absorbed will be converted to more power for her weapon.  Zarya can also put a Particle Barrier on one of her teammates as well, which further makes harassing harder for Tracer.

Zarya can also use her Particle Barrier on herself or one on of her teammates to save them from Tracer's Pulse Bomb, while at the same time absorbing all the damage and converting it to make Zarya's weapon much more powerful.  With this in mind, it's important to make sure Zarya has used her Barriers first and it goes on a cooldown before using your Pulse Bomb on her.

Since Tracer is usually out harassing and flanking, she is usually in the clear when Zarya uses her ultimate Graviton Surge (clumps all the enemies up in the area).  However if Tracer does get trapped in Zarya's Graviton Surge, she can just use Recall to escape out of it or use two quick Blinks as well.

As Tracer, you are better off avoiding Zarya and focus on killing other easier targets, but getting some open shots on her is a good idea if you can.

D.va:  D.va's Fusion Cannons are very powerful up close, which makes attacking D.va as Tracer somewhat difficult.  D.va should not be a prime target for Tracer as D.va has too many hitpoints and she can use her Boosters to get more health or escape from Tracer very easily.  D.va's Defense Matrix can prevent Tracer from doing some short term damage to her as well as blocking Tracer's Pulse Bomb.

D.va's ultimate (Self-Destruct) is not a big deal to Tracer as she can simply blink away from it.  D.va can also survive a Pulse Bomb hit, and even if her mech dies, D.va will still live and call down another mech.  Overall a tough fight for Tracer, but you may be able to pull off some harassing shots at her to throw her off track a bit and to charge up your ultimate.

Tracer:  Fighting another Tracer is a battle of who has better overall skill at aiming with the Pulse Pistols and blinking around to make a harder target and Recalling at the right moments to escape to refill life.  Remember using Recall can save you if another Tracer throws a Pulse Bomb on you.