The point of Overwatch is playing as a team, and some heroes work in combination together better than others. It's all about striking the right balance. Here are our favourite synergy combos of the bunch, for maximum mayhem, destruction, and match-winning shenanigans.
We'll start with an obvious one; so obvious, in fact, that you've probably seen this pair flying around a map together already. Pharah's weapon has a slower rate of fire than some of the other heroes', but the damage is high and enemies can get caught in the splash damage even if you don't score a direct hit. Boosting Pharah's damage with Mercy's staff makes her much more deadly, especially on Pharah's ultimate attack, plus you can switch to healing to make sure she stays in the fight.
From a Mercy point of view sticking with Pharah gives you the chance to pick up a bunch of good assists. Because Pharah's got a jetpack, and will often be further from the enemy or in the air, you can use Mercy's Guardian Angel swoop to get a quick escape if you're in trouble (which you will be, because a competent offense will make it a priority to take out an enemy Mercy).
McCree is good on the front line, providing he has a bit of back up, because he's deceptively squishy and often ends up in kill-or-be-killed fights. If you're playing as McCree you can team up with a Reinhardt to take potshots from behind his shield whilst staying out of harm's way. This is doubly useful if you're launching your ultimate ability; it can take out an entire team, but it takes a few seconds for McCree's shots to lock on, so he can be vulnerable in the run up. Not so much if he's got a big ol' tank protecting him, though.
Roadhog and Junkrat are canonically a team in their origin story for the game, so it's nice to get them back together again. They do actually work together pretty well, though. Junkrat and Roadhog are both good at pushing and pulling baddies around, and if you're communicating well you and a mate can use them to drive the enemy team into each other's attacks. Junkrat can lay down a blanket of grenades to scatter people and send them running into Roadhog, whilst a rampaging Roadhog can turn them back into said grenades, or use his hook chain to pull enemies into Junkrat's traps.
Putting these two grubby Australians together can cause general panic and alarm. The downside is that they're both on the slow side, so you might want to bring a Lucio into the mix to give them a bit of a boost.
Reaper deals high damage quickly, so by combining that with Zenyatta's Orb of Discord debuff you can destroy the enemy (plus Zenyatta just needs a line of sight and doesn't have to get too close to the action himself). Reaper will still get the benefits of Zenyatta's Orb of Harmony healing while he's in his Wraith Form, so he'll get the dual benefits of healing and avoiding damage at the same time, and won't have to move too far from the enemy or run off to get a health pack.
Torbjorn is impressive to come up against even by himself, but if he's coordinating with a Widowmaker then they can stop an entire team. If Torbjorn sets up with a well placed turret then Widowmaker can find a sniper perch across the map opposite or a little to the side of Torbjorn. When the enemy run into Torbjorn and his turret they'll either slow down or try and take cover, but either way they should now be exposed for Widowmaker to make an easy shot. Widowmaker's ultimate is also super useful for Torbjorn, because often a flanking hero like Genji or Tracer will be trying to sneak around to take him out, but if Widowmaker has given him Infra–Sight they won't be able to get the drop on him.
This is pretty beautiful combo to dust off right, especially on an Escort game. Have one player plant as Bastion in sentry configuration, setup Reinhardt with the shield to shield Bastion from oncoming damage, and have the Mercy buffing Bastion for extra damage. Watch the enemy fall before you, as ripe wheat falls before the scythe of the reaper.
Zarya is a difficult tank to play as, because you have to be much more tactical than with the others, but teaming up with a Tracer is usually a good bet. Zarya relies on absorbing damage through her barriers to increase her own damage output, and Tracer is super fast and will draw some fire while she's attacking, but has low health. Solution: whap a barrier on Tracer for mutual benefit.
Bonus points if you form up with a Lucio. His passive heal can help Zarya and Tracer when the barriers are on cooldown, and if he's boosting Tracer's speed while she's got the barrier she becomes ridiculous.
Zarya's ultimate is a gravity bomb that pulls in and traps any nearby enemies. If this is well placed, and combined with literally any hero ultimate that has an emphasis on damage, then you're golden. Hanzo's dragons, Tracer's grenade, McCree's Deadeye, Pharah raining justice from above, Junkrat's RIP–Tire, D.Va's self destruction: they're all devastating on a group of enemies, and if you've used Zarya's ultimate then they can't un–group.