All the SSF2T versions are Really Hard to beat Especially the initial version and 3DO (although Mountain Breaker and his USF2 theme is up there for sure)
And then there's "Shura" ahh It sure makes me wish Asura's Wrath got remade or just to see more of the Best Angry Dad of all time (sry Kratos your more chill these days) updated to the RE Engine