OW Hero: Mei

Complete hard counter. Mei will win 100% of the time unless Symmetra opens with a fully charged right click and has a turret nest nearby. Mei can easily iceblock to mitigate a charged beam and will freeze/headshot every time. Unquestionably the most difficult encounter as Symmetra.

This one is close, but if Symmetra can bring the fight into her sentry turrets there is little Mei can actually do to win that fight. The fact that Symmetra's close range attack also tethers means she will be able to get damage on mei for a longer time before getting frozen than other characters who require precise aim.