i think bastion is silly; i wait until he gets out of blaster mode then he is a lot easier to deal with. you can also spam ranged cc. its a bit more difficult when fighting for space or if he is being hard pocketed / covered for by tank, but if you play dive you might be able to get some cheeky trolling on bastions after they grenade jump or get out of turret mode. mauga can troll him too, and anybody with projectile eating abilities can stall his turret form
Bastion is fun, BUT one Hanzo can completely ruin Bastion’s day. 
Zen to some degree too.
You don’t even need to be any good on Hanzo. Just shoot in the right direction.
Zen is a good support counter. Obviously you need to not peek his turret form, but as soon as he’s out you can pop discord on him and melt him.
Ana as well if your team is disciplined enough not to shoot him while he’s slept.