Z (SPOILERS)

Upon defeat, Ouroboros tells Z that there's no way to change the future if it's kept eternally in place, but Z doesn't listen to a word they say, and believes that the only way left to keep an unknown future from coming is to destroy the entirety of existence itself, while childishly proclaiming that he hates the entire world, proceeding to then jettison Aionios into oblivion.

Example of:
Suicidal Cosmic Temper Tantrum