The movie He Never Died isn't exactly full of exposition. In particular the leading character, Jack, is taciturn and says very little about who he is or why he is behaving the way he does.
We see many hints that he is very strong and immune from injuries that might kill him. In an early scene we see his shirtless back which has two scars that hint, perhaps, that he might be an angel whose wings have been removed (like Lucifer Morningstar in Lucifer).
But later in the movie he says several things that cause further confusion about his identity. Answering a question about how old he is, he claims to be in the Bible. He also says he doesn't know whether he had a father and mother. But he then claims to be Cain (the first murderer) and acts as though he has been cursed and wants to die.
But if he is Cain he is human. If he is human he has a mother and father, so he seems to say contradictory things. But, on balance, the intent seems to be that he is Cain. Cain was not an angel. So what were the scars on his back?