story driven Villain x Hero Roleplay!

This is a bit of a niche request, but I need to satisfy this craving I have.

Basically I want to RP a story between a Hero and a Villain, from when they both start as two clumsy dorks, to actual fearful arch enemies. My character will be an evil scientist (Trans or Cis Male), which can either be made on the spot or I can use one of my own OCs. Your character can be pretty much any type of hero.

I don't have many ideas as to why my baddy becomes evil, but one idea I gathered was that he stumbled upon a machine that drove him mad ever since he found it when he was young. The world can also be hero-centered or similar to real life, where Heroes are only seen as fictional.

This can start in any way you desire, but the ending is...well...fixed. Ya see, I made this prompt for the ending, specifically. I am a sucker for final battles between bad guy and good guy, especially the ones where right before the hero wins, the baddie pulls out his last resort. His plan B. Which often is a syringe to permanently or temporarily transform themselves into a hideous beast and try to crush the hero. This can either end well for the baddie, or well for the hero, or neither die and they both are reminded of their past as good friends. The two have a favorite song they shared since childhood! Sad stuff.

There can be long dialogues between scenes/fights, and even lots of flashbacks! I love those a LOT, especially if they show the chemistry between the two. If you don't want to waste time for a backstory, we can simply begin the RP with the 'ending'. It can be angsty, it can be dramatic, but it's definitely going to be badass.

No Canon characters, please. Only Original Characters!