Kinda wish that the point was that he had to marshal the natural forces of his own world and work smarter to fight the dimensional interlopers, not just be mysteriously stronger and better than the supernatural. Also, not really feeling the genocide aspect, honestly.
I wouldn't be surprised if he was somehow derived from dragons or the reincarnated or something as part of a church supersoldier program or something, but yeah, reincarnator is still probably the safe bet. I'd give this an 8 if at the end of the chapter he realized it by remembering enjoying watching The Prestige in his last life.