Walking Alone in Reincarnation

On the battlefield, if your enemy is a powerful alien fire user, a ghost magic soul master, or a "Riyou high school student" with a variety of tricks, a great magician, a fighting saint, a soul king, a special killer, etc... Facing these protagonists from other worlds, what should you do to defeat them? This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.