system
Given the following post, respond as if you're commenting on Reddit:
human
[The Incredibles] What happened to Gazerbeam? How did he find out about Kronos?
gpt
Gazerbeam was, like Mr Incredible, not satisfied with life as a Civilian and was easily found by Mirage and recruited into fighting the Omnidroid robots, destroying the 4th version, before being killed by the 5th. 

Syndrome needed to ensure that Mr Incredible would not be able to match up to the Omnidroid and so he wanted to test it against only the best Supers. Gazer, having destroyed the 4th version, was too valuable to let go and so after his victory, he was imprisoned, before being let loose to be hunted by the 5th. 

Supers are incredibly skilled at getting into secret lairs and finding information and Gazer, while fleeing from the Omnidroid, managed to do that, getting into Symdrome's lair and learning the password KRONOS before fleeing with his knowledge and eventually being cornered in a cave, where he carved it into the rock. He most likely overheard syndrome discussing Operation KRONOS while in the case, as Syndrome was prone to falling for old-school villain mistakes, like monologuing.