Berserker is generally considered unhinged, & takes a twisted kind of enjoyment from fighting, showing off the full extent of his overwhelming power. They're still able to cool off somewhat, but not a whole lot.

Sounds a lot like a villain when overcome with his bloodlust, often laughing a bit maniacally during combat & provoking the opponent constantly, but is otherwise surprisingly tame when he's in a calmer state of mind.

You can find a quick preview video of the character here.