system
Given the following post, respond as if you're commenting on Reddit:
human
[Marvel] why did the kree ever start hating skrulls in the first place?
gpt
The Skrulls came to the planet Hala, which had two sapient races. The Cotati, a race of intelligent, pacifist tree people, and the Kree, a race of primitive, violent primates. The Skrulls were a peaceful race at the time, wanting just to trade, but needed to figure out which of the races on this planet they should deal with. 

They picked 17 Kree and 17 Cotati, and gave them a competition. Each group would have a year on an alien world to build something amazing, and then the Skrulls would use that to decide which one was the actual dominant species on Hala. 

The Kree were dropped on Earth's moon, where they built a city, with its own atmosphere and higher gravity. The "Blue Area of the Moon" that would later become home to Uatu, the Watcher. 

The Cotati were dropped on a distant planet, and turned a desolate wasteland of a barren world into a thriving lush garden. The Skrulls acknowledged that terraforming an entire planet was more impressive than making a city, and decided that they would trade resources with the Cotati. 

The Kree got upset at the whole thing, killed off the Cotati, and then with the Skrull technology they'd gotten ahold of, decided to kill off the Skrulls as well for shaming them in such a way. The Skrulls responded with military force, which over the centuries changed their society from the peaceful traders they had been, to another military power in this galaxy.