I feel as if your journey from writing him as a psycho villain to having him as part of the main cast has got to be a much weirder one than, for me, just not thinking about him at all until my brain did a sudden 180 into The Abyss Zemo-and-BuckySam-land this summer. In fact I'm having some amount of trouble thinking of other times when that's happened to me, having one characterization (or role for a character) get firmly established and then having it abruptly change. I mean, I love villain redemption arcs, so it probably HAS happened, but usually not over installments of canon happening across a series of years, generally more like in whatever time period it takes me to watch the canon in the first place.

But as far as writing a character as a villain and then having them migrate to ally or antihero or whatever in future installments of canon ... I'm drawing a blank on times it's happened in my active fandoms with characters I was currently writing! Maybe Jack, a little bit, since he went much harder Team Carter in season 2, but I was already writing him that way anyway. XD