Alekzi
I'm seeing a lot of people speculating, but first of all we need to know which version it is and which spirit is possessing it. It's likely to be the movie version as the comic book version is strong enough to fight the Hulk. Even though it's from the movies, I imagine it has the same powers as the comics, only weaker. It's also important to note that even though the human form is weaker, the Rider's powers are automatically activated at risk to life. Killing him in human form is almost impossible, even weak he will still regenerate instantly if he hears risk to life. It's also important to consider that the MC can train to master a part of the Rider's powers. I don't know enough about Rider to say if it's possible to master one's own spirit of revenge. Congratulations author, I think this is the best twilight fic I've ever seen. No over-the-top drama, no over-the-top teenage angst, no full sentences describing what the MC is like a god. Just a little romance, action, fantasy and drama. The MC gets extra points for not being a copy of Sasuke.