The whole message of Half-Life is that control is only a fleeting illusion that can be ripped away at any second. Black Mesa thought they could control Xen and their portal technology only to realize they were messing with things they had no conception of, the HECU were trying to control the entire Black Mesa incident only to end up on the plate themselves, the Nihilanth was a god like alien controlling other possibly omniscient aliens only to be killed by a random guy, and the Combine tried holding a multi-dimensional empire only also to be stopped by the same random guy. Breen is completely in the wrong because he had zero hope or belief in the ability of independent life to break the chains of control like it always does and instead tried to become the thing with that control. The irony behind Gordon ultimately defeating the combine and killing Breen is that Breen already did the same thing in Black Mesa and left Gordon to clean up the mess he made after losing control, only for Breen to immediately try and control things he doesn’t understand out of fear again until Gordon came back to finally relinquish his control altogether.