deter another large-scale Russian offensive after any ceasefire

Russia is fighting to prevent NATO troops in Ukrain. Am I mistaken or does this bind Russia to fight until they either collapse or conquer all of Ukrain?

Life will find a way. Going back can be used to create nuclear winter but even then, life will go on.

To completely screw over the world, I would go into the future and acquire the source code for a general AI.

Then the world can be locked down and robots can be built to abuse every human and sentinent being individually, for a very long time.