Here's a narrative throughline to use with the Cheetah:
Barbara Minerva is Evil Lara Croft, doing whatever she wants to find ancient artifacts, and then either keeping or selling them, with no concern for what harm comes. This leads to conflict with Diana, who tries to stop that kind of thing. She does so, repeatedly, but is otherwise fairly gentle with Barbara, because Diana views her as wayward more than malign. This actually irks Barbara, a lot, because she sees it as demeaning. And so she seeks to get enough power to fight back, and actually beat Diana. She does so, merging with the power of an ancient god and becoming the Cheetah.
At this point, she feels like she's free to ignore and disregard Diana. She does her usual routine, only when Wonder Woman show's up to stop her, she transforms into a cat-beast, and fights her to. . . lets say a victorious draw, the kind where Diana doesn't lose, but she is driven away enough that Barbara can continue her business. This emboldens her, and she starts getting even more reckless in her artifact-mongering, since she "doesn't need to fear anyone anymore".
This goes about the way you'd think, as she eventually bites off more than she can chew, and unearths or sells or whatnot some artifact that isn't just evil, but really really disastrously dangerous. She thinks she has everything under control, and then finds out how wrong she is, and stuff she cares about ( whether personal possessions or personal associates ) are the first to suffer for it. She then has to swallow her pride, and outright go to ask Diana for help. Which Diana gives, and while she's uncompromising in her judgement of the situation, she also offers an open hand to Barbara.
At movie's end, the disaster is averted, and the day saved. Barbara Minerva. . . is still the Cheetah. And she's still an amoral artifact hunter. But. . . she shows definite signs that she's not as callous and amoral as she was before. Is she still a supervillain? In the general sense, sure; maybe even end the movie with another clash between her and Diana. However, *Diana* thinks that she's made a major step forward, and approves of this. And hey, just because you haven't fully redeemed doesn't mean that each little step of becoming a better person isn't worthwhile.
