Tracer in close quarters can melt you and is impossible to get a bead on, Mei's ult, Bastion in general, the girl that can spam Rockets, D. Va's ult, McCree feels unplayable.
Tracer is squishy as hell, you just need to learn what she can and can't do in order to play against her effectively (or in the worst case scenario you can run to a safer location). For instance, she disappears completely when she recalls, so when that happens just think back to where she was three seconds ago. When it comes to her blinking, there's a flash of light that tells you where she blinked to.
Mei's ultimate can be avoided with many mobile heroes (Genji, Tracer, D. Va, McCree, Soldier, Pharah, Winston, and a few others all have the capability of escaping it before it's too late). Plus you can just walk out if you're near the edge.
Bastion is extremely weak and probably one of the worst heroes when playing in a high skill bracket. He's remarkably easy to shut down after you start to figure him out.
Pharah can be hooked by Roadhog and her rockets cannot penetrate shields. Her ultimate is a bit powerful, but a good sniper can make quick work of her.
D. Va's ultimate, while powerful, cannot kill you if you're behind some sort of obstruction. However, keep in mind that good D. Va players will probably send the Mech flying forward/up in order to decrease the time you have to react.
McCree is built around the flash bang, fan the hammer, roll, fan the hammer combo. He can destroy anyone in a 1v1, but struggles to take on multiple people and is severely less effective if his flash bang misses.
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