There are more elaborate Alduin mods that add a lot more to the game than this, but this is personally something I've enjoyed a long time after tweaking the worldeater to something that felt genuinely frightening. There are 4 versions, each with slightly different sizes and hitpoints, but the largest recommended version has his hitpoints above 17,000... Now your godlike character can face a final foe worthy of an epic battle without changing anything about the core game experience.