Doomsday Rescue from Scratch

Just like the male protagonist in the re0 anime, he has gained the ability to return after death infinitely, but every time he returns from death, he is faced with the end of the world. How can a modern ordinary college student without any magic or any technology use his abilities to save a world-ending crisis? This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.