Aside from broken DLC characters, there's only one true "pay to win" fighter that I can recall:
The free to play Tekken: Revolution
You could buy in-game currency with real money and enhance your characters. I never played much of this game because it was so fucked. You would regularly see piss easy death combos simply because someone had power leveled their character so much. Here's a quick video:
I'm not sure what the purpose of this game was (aside from Eliza being basically a beta test for the 2D characters added in Tekken 7), but I'm so happy they didn't go this route for Tekken 7.