One of us is constantly beating the crap out of everyone else with a particular character? Switch it up.
Or learn to counter whatever they’re doing to win.
Dhalsim’s endless string of “Tiger!Tiger!Tiger!Tiger!Tiger!Tiger!TigerUppercut! You! Win!” was eventually conquerable with the right combination of moves and that wasn’t even player skill, it was a shortcoming in the game’s internal timing (that was bad enough that it overwrote the existing playing sound effect while you were doing it).