I feel.like the words "he broke" or "mentally broke" get thrown around too much, or often tend to be improperly applied to just a guy who is gassed out... however
Khabib is the clearest example of a fighter whose opponents looked like they were overwhelmed, panicked and clearly had no answer. And he did that to elite guys.
By the time he wax champ he had improved his submission threat to mercifully offer a way out, but on the way to the title he just beat the stuffing out of guys. Edson Barbosa and Michael Johnson come to mind. Khabib trash talking while.mauling guys was something to see. "You know I deserve this shot, you know this."
That's gotta be traumatic when the guy whooping your ass is giving you a lecture mid whooping.