I've seen/read a few isekai where a character from "our" world is reincarnated as the villain of a fantasy world s/he's familiar with but none of those had that character leaning into villainy in the new life at all, partly because they care about the other characters (even in some cases where they don't necessarily see them as real people) and sometimes because the villains canonically met bad ends the reincarnated person wants to avoid.