It may well be a cliché, but it's Chun Li for me:
I could always easily get into her fighting style, whether it was in the 2D Street Fighter games, the 3D games, or in Capcom vs SNK. Especially in the latter, her super combos are devastating. I remember at times being stumped on how to defeat a boss or a mid-boss, and just switching to Chun Li and have her wall jump give me the edge. That's how I first defeated Vega (Spanish), at least. Beating him at his own game.
I also like her back story, how she seeks justice for the death of her father, how she ends up training a bunch of kids in the martial arts, and how -at least in the games- she doesn't seem to be romantically linked to anyone (besides MAYBE Nash), even if other media try to pair her up with Ryu or Guile. She always came across as a highly independent character with the greatest sense of justice among all of the Street Fighter participants, a neat look with the yellow pattern on the sky blue China-dress, and her hair with the half bangs and the double buns.
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clarity of thought before rashness of action