Pharah:  Soldier 76's weapon is very powerful even in longer ranges (even with fall-off distance damage), and makes firing down a Pharah relatively easy for him.  Pharah's rockets can do some damage too but Soldier 76 can use Biotic Fields to heal that up along with the option of getting under something to block her away from him.

Pharah's ultimate Barrage can be countered by a quick Helix Rocket then a few rifle shots from Soldier 76.

Pharah is a great target for Soldier 76's ultimate Tactical Visor, as it will auto aim at her as she's flying around in the air.  The best thing for Pharah to do in this situation is to immediately drop down (stop hovering) and quickly lose line of sight with Soldier 76's aim bot.

Tracer:  Tracer can be annoying to deal with, luckily Soldier 76's pulse rifle is one of the better weapons to use against Tracer (not too great though against her).  If you decide to use a Helix Rocket at her, I find aiming at the ground in front of her seems to be the best way to go about it.  Using Tactical Visor (ultimate) against Tracer is very effective, as you will automatically keep aiming at her even while she is blinking fast.

Tracer's Pulse Bomb and Recall combo is deadly against Soldier 76, as there is nothing he can do to counter it.

Mercy:  Even though Soldier 76's flanking abilities are not as good as some of the other offensive heroes, I find Soldier 76 does fairly well against Mercy.  She is a prime target for your Helix Rockets, and she is usually in medium to long range which is great for Soldier 76's pulse rifle.

When using Tactical Visor, Mercy is the first enemy you should be aiming at.

Zenyatta:  Zenyatta's Discord Orb is very deadly, but I find with Soldier 76, it is less of an issue thanks to his Biotic Field (healing) ability.  Just try not to get overwhelmed by to many enemies at once and you should be able to survive.  Soldier 76 can also quickly Sprint behind a wall to lose the Discord Orb and his ultimate Tactical Visor can be used to focus fire on Zenyatta to quickly kill him to remove the orb.

Zenyatta moves slow, so it is easier to aim Helix Rockets at him.  Use Tactical Visor shortly after Zenyatta uses his Transcendence ultimate.  I find it is important to always keep in mind when Zenyatta uses his Transcendence ultimate, because it will pretty much cancel out Soldier 76's ultimate (Tactical Visor) at the same time.

Roadhog:  Since Roadhog is such a big target, Soldier 76's Pulse Rifle works very well at nearly all ranges against him.  The main thing you need to watch out for is getting Chained Hooked.  Keep your distance from Roadhog to avoid getting hooked, if you get to close to him, consider sprinting away from him if you can.

Roadhog is a prime target for your Helix Rockets, as he is big and slow moving, which makes aiming Helix Rockets at him very easy.

Since Roadhog is a tank with high HP, avoid wasting your Tactical Visor on him and focus on taking out non tanks first.  Tactical Visor does NOT get canceled if Roadhog Chain Hooks you, but you still have a high chance of death with his Scrap Gun shot with melee combo.

Bastion:  Soldier 76's poor map mobility makes dealing with a Bastion somewhat difficult.  You may be able to dish out some damage from longer ranges to a Bastion Sentry with your Pulse Rifle, but getting behind him can be difficult, although your Sprint ability might be able to get close to him depending on the map and the situation.

Helix Rockets are very powerful against a Bastion Sentry since aiming them will be very easy on stationary targets.

Tactical Visor can be deadly against a Bastion Sentry, but I really only recommend using it against him if his health is already somewhat lower as he has 300 HP while in Sentry mode and it can be a waste if you will be unable to take him out during Tactical Visor.

Reinhardt:  Reinhardt's massive shield is a problem for Soldier 76.  There isn't a whole lot Soldier 76 can do to Reinhardt, it's tough to get too close to Reinhardt due to his Charge ability along with his powerful melee hammer and ultimate (Earthshatter).  If there isn't any other enemies to shoot at, then taking down Reinhardt's shield is the only option.

Zarya:  You need to be extra cautious with Helix Rockets around Zaryas, because if you throw a Helix Rocket (or shoot your rifle) at a Particle Barrier it will be blocked and will greatly enhance the damage Zarya does with her Particle Cannon weapon.

Zarya's short range beam does more damage than her longer range charged explosive charges to a single target, so keep your distance from her while using your Pulse Rifle on her more so than Helix Rockets.  Use Sprint to reposition yourself away from her.

Soldier 76 is usually in range to be targeted for her ultimate (Graviton Surge), so it might be a good idea to move around the map in unpredicted areas to avoid being trapped by her ultimate.  If you get caught in the surge, your best bet is to throw down a Biotic Field and hope for the best.

Tactical Visor is generally not good to use on tanks, but Zarya would be the best tank target for Tactical Visor since she has poor mobility and lacks the most with blocking, healing or HP of any tank.  Just watch out for her using a Particle Barrier to counter it.

McCree:  DO NOT come in close range with a McCree, he can quickly and easily kill Soldier 76 up close with his Flashbang and fan fire attack.  At longer ranges Soldier 76 will have the advantage.  A good McCree player will use combat rolls quick enough to avoid Soldier 76's Helix Rockets.  If you hear McCree use his ultimate, you can simply sprint away behind a wall to avoid it.  NOTE: enemy McCrees will yell "Its high noon time" to warn you when he uses his ultimate.

Ana:  Ana does weak damage overall with her Biotic Rifle, this along with her poor mobility can make it easier to target her for some easy damage.

However, the biggest advantage Ana has over Soldier 76 is the ability to shut down his Biotic Field with a Biotic Grenade.  Biotic Fields are stationary healing sources and allies will be tempted to gravitate towards it for healing, Ana can simply throw a Biotic Grenade at the allies trying to get healed by it and the grenade will prevent Biotic Field's healing for a short while on those allies.

Soldier 76's Sprint ability and superior mobility during his ultimate makes him not a prime target for Ana's Sleep Darts in general.

Ana's slow mobility could get her caught in the midst of Tactical Visor if she can't find a wall to get behind in time.  Ana can throw a Biotic Grenade on Tactical Visor which will make Soldier 76 more vulnerable while using it.

Soldier 76 can deal with a Nano Boosted enemy (Ana's ultimate) by simply sprinting away from it.

Hanzo:  Hanzo can be deadly to a Soldier 76, as it only takes one good shot to the head with an arrow and your dead.  Biotic Fields help to reduce the extra damage done by Hanzo's Sonic Arrows, just remember to use the Biotic Fields around corners where you and your teammates can take cover and fire at the enemy at the same time.  If you get to close to Hanzo, keep jumping to further avoid his Scatter Arrow shots.  You may need to sprint away from Hanzo's ultimate Dragonstrike.

Soldier 76 can avoid Hanzo's Dragonstrike by sprinting away from it.

Soldier 76's ultimate Tactical Visor can be deadly to Hanzo.  Hanzo can try to avoid Tactical Visor's aimbot by losing line of sight with him, possibly by climbing away.

Widowmaker:  The problem with Widowmaker for Soldier 76 is she is usually much further away and it can be difficult to damage her from long distances.  You can attempt to lob a Helix Rocket at her, but she can strafe around to avoid it, and the pulse rifle is only mediocre at best for long ranges.  You will need to do pulse shots at her from long ranges (rapidly pressing the fire button) to increase accuaracy.  Flanking her with Sprint is possible, but only under rare circumstances.

Soldier 76's ultimate Tactical Visor can be very deadly to Widowmaker even from long range, as his shots will always connect to a target, and Widowmaker should be one of his prime targets during Tactical Visor.

Mei:  Since Soldier 76 is usually a distance from his enemies, he doesn't have to worry too much about Mei freezing him in close range.  What you have to worry about the most is Mei's Ice Wall.  Ice walls can block your Pulse Rifle shots, especially while using your ultimate (Tactical Visor).  As soon as Mei uses her ultimate (Blizzard), quickly find out where the center of the Blizzard is at (you will see a little floating spinning device), and sprint away from it to avoid it.

Genji:  Close matchup.  Biotic Fields and good pulse rifle damage will help you take on a Genji fight.  You will need to watch out for Deflect and only use Helix rockets after Deflect is used.  If you hear Genji turn on his ultimate (Dragonblade), I find it's usually better to just sprint away from it.

Deflect is very effective against Soldier 76, especially when you use Tactical Visor.  Deflect has a chance to take you out if enough bullets get repelled back at you.

Lucio:  Soldier 76 doesn't have to worry too much about Lucio's sonic projectile spam thanks to his Biotic Fields.  Since both heroes tend to stay a distance form each other you don't have to worry about getting knocked back by Lucio's Soundwave ability.  However, Lucio's healing and speed buff aura will make dealing with him and his team more troublesome.  It will be harder to aim your Pulse rifle and Helix Rockets at Lucio when he has his speed aura on.

Just like Zenyatta, I find it's important to always keep in mind when Lucio uses his Sound Barrier ultimate, because it will pretty much cancel out Soldier 76's ultimate (Tactical Visor) at the same time.  So try to use Tactical Visor shortly after Lucio uses Sound Barrier.

When Lucio uses Sound Barrier, you are better off just taking cover until their shields degenerate back to normal, which will take about 5 seconds.  You can use Sprint to reposition yourself during this period of time.

Torbjorn:  Helix Rockets work really well on Torbjorn's turrets, and Soldier 76 is a decent counter to Torbjorn for this very reason.  Biotic Fields help to negate any damage done by turrets as well. 

However, since Soldier 76's mobility is not as great as heroes such as Reaper and Tracer, he will have a much harder time taking out Torbjorn himself, and a lot of times Torbjorn will be able to repair his turret faster than Soldier 76 can deal damage to it, thus Soldier 76 will usually need help from his teammates to take Torbjorn and his turret out.

If Torbjorn uses his ultimate (Molten Core) and he is repairing his turret, I find it's practically useless attacking the turret since he will be able to repair it so quickly. Instead, I find it more effective at attacking the Molten Core Torbjorn himself in this case.

Junkrat:  Knowing how to use Sprint around Junkrat is the key to dealing with him properly.  If you know the enemy has a Junkrat on their team, you need to be extra cautious when sprinting around corners or other obstacles because you may find yourself sprinting right into a Junkrat Trap/Mine before it's too late.  When you hear Junkrat use his ultimate (Rip-Tire), you should quickly figure out where it's coming from and sprint away from it.  NOTE:  Junkrat will yell "Fire in the Hole" when he uses Rip-Tire.  If you know it might be too late, then throw a Helix Rocket at the tire to attempt to kill it, especially if you know it will save your teammates too.

Symmetra:  If you know the enemy has a Symmetra on their team, you need to be extra cautious when running into her Sentry Turrets, which are usually placed in hallways, smaller rooms, or behind choke points.  Luckily, Soldier 76's Pulse Rifle works well at taking her turrets down.

It usually isn't Soldier 76's job to hunt down Symmetra's Teleporters, but you can always sprint around the map to find and kill one if you need to, especially if you have a strong suspicion where one might be.

Tactical Visor works well on Symmetra due to her poor mobility to take cover from it and her low HP of 200.

Winston:  Winston himself isn't much of a threat to Soldier 76, but his ability to protect his team with Barrier Projectors really makes it hard for Soldier 76 to dish out damage with his Pulse Rifle.  It usually isn't worth it to try and kill the barrier, because (unlike Reinhardt's shield) it will automatically disappear after a short period of time.  The short periods of time when the Barriers are not up is prime time for Soldier 76 to deal as much damage as possible.

Since Winston has a large hitbox, Soldier 76 will be able to do a lot of damage to Winston even from long ranges thanks to the fact that you don't need to do pulse shots to manage recoil as much.

If you see Winston use his ultimate (Primal Rage), just sprint away from it to avoid it.

D.va:  It's best to keep your distance from D.va as her Fusion Cannons are more powerful close up.  Remember, Soldier 76's Pulse rifle does fall-off distance damage with poor accuracy at long ranges, but with bigger targets like tanks such as D.va, firing at long range can be effective against her.

Helix Rockets can work good on D.va as long as she doesn't block it with Defense Matrix or escape it with her Boosters.  D.va can also use Defense Matrix to stop incoming shots from Soldier 76's ultimate (Tactical Visor), or even use her ultimate Self-Destruct to nullify Tactical Visor as well.  The better time to use Tactical Visor is after D.va ejects from her Mech.

Reaper:  Soldier 76 usually sticks around his team to support them with DPS and healing and doesn't usually come in contact with Reapers 1on1 a whole lot. Reapers can attempt to flank Soldier 76 from behind which can result in a kill. However, Soldier 76 can sprint away from a Reaper to avoid his damage.

Soldier 76:  Dealing with another Soldier 76 is a battle of who has the better aim with the Pulse Rifle, and who can land their Helix Rockets better.