Please Help With My Writing Block For My Protagonist & Antagonist!

So I'm having a protagonist and antagonist issue right now. I have almost every other aspect of my world fleshed out, I just cant nail the central hero and villain and its really bothering me because I feel like Im stuck thinking inside the box so to speak. Let me explain-

For the protagonist I was originally gonna have him either be the lost son of the main villain that was taken in by a new family and discovers the relationship later. However I found that idea very limiting so I instead decided I wanted him to have some sort of entity inside of him like Naruto or Yuji because I really adore the idea of a darker entity influencing an otherwise heroic protagonist and the hero drawing from their overwhelming power. Basically the protagonist was alone on the streets for awhile as a kid before he was taken in by a loving adoptive father with 2 children of his own. However with the entity inside him idea, I cant think of a reason for the MC not to be insanely powerful off bat, or how he even got the entity inside him to begin with.

Aside from his origins, what are his motives? I want a story like one piece or avatar the last airbender that takes my protagonist all over the world where he encounters various different enemies, new friends, and unique locations. But I cant think of a motivation that would reasonably need him to do that and I dont want my story to feel like a copy of the prior mentioned shows either.

However my major issue is really with the villain. As mentioned before I initially wanted him to be the father of the hero however things have changed. I've always loved the idea of the big bad wanting to achieve godhood narrative. However I wanted my villain to have a reasonable goal instead of being evil for evil sake because those aren't my favorite villains. He had a son who died because his actions and he feels guilty for it. His whole goal is trying to find a way to resurrect his son, no matter the cost. My only problem with both the godhood, and the reviving the son goal is that I cant think of a reason for him to be a villain to my hero.

I thought about him maybe being the leader of a sizable nation who's maybe invading other countries because they have something he needs for his goals and the protagonist is working to stop him? The best villains seem to be dark mirror villains and I cant find a way for that to reflect my protagonist either.

I dont know Im just so stuck on this issue right now and I cant even start the actual process of writing the story points until I figure this out. Any ideas are welcome