I think most of them have stayed pretty consistent, they're not terribly complex in terms of personality or backstory. Usually I have a specific idea in mind when designing them, and their personality or character design tend to inform the other.
To answer the question, I think it would have to be Marcus, a D&D character of mine! He mostly lives on my fanart account but I sometimes RT stuff to this profile. Until I put him in BG3 I never imagined him bottoming or subbing for anybody, but then Astarion and Haarlep happened and I can't stop drawing him getting mindfucked.
He hasn't changed -that- much, because he was always a hedonist and prone to rash decisions, but I like exploring this side to him that maybe struggles to come to terms with how trusting someone to take care of him while in a vulnerable position (through hypno or vampire bites) makes him feel safe. I also enjoy overconfident subjects getting dommed and he's the perfect candidate for it. Sorry for the long answer but thank you for the interesting question!