Once upon a time, a man named Peter Parker had enough. "Activate Ultrakill!" he yelled to EDITH. Then he went to NYC and went on an omniman spree. He sure was happy to see his favorite color everywhere as he sang "Paint the Town Red" by Doja Cat. The Avengers tried to save their friend but he could not hear through the ultrakill. One by one, they all lost their lives trying to calm him down.
More superhero groups were dispatched, but they all met the same fate.
Once he had killed all potential threats, he went to the top of burj Khalifa and declared himself the new ruler of the one world union. When people protested, Peter officially had enough. He activated Final Ultra kill and exploded, shredding Earth into a billion pieces and leaving all the few survivors to float in space as their blood boiled and exploded.
This is the origin of the word "ultrakill".
The End.