it was actually not that difficult when u try for like 4 or 3 hours. I only used the M. Bison special power, dont remember the name, the whole time, for me ken, sagat, and balrog, were a litlle bit of a problem, but u have tu learn their moves, and do the bison thing.
If ur fighting ken just be careful not to jump and kick him that even if ur brain wants to dont do it, and when u do the Bison thing try to do it exactly when his gettin up right after he falls down cause if u do it before, he'll use the dragon punch and punch in the nuts.
Be patient and keep trying. i just bought the game 2 days ago and i already have the achievements.
Veni Vidi Vici