>>47353363A big part of it is anger problems. Other team leaders could control their tempers reasonably with the minor exception of Lysandre right after being defeated. Guzma also seems to be pretty violent and has definitely beaten on people in the past, but he never really threatens it within the actual game outside the context of a Pokemon battle.
Ghetsis on the other hand flies off the handle and threatens people with violence from himself or his Pokemon all the time, including and especially children. He slams his cane around like a raging geriatric in BW2 more times than I can remember, even to the detriment of his own health judging by the labored breathing in that BW2 sprite. It should also be noted his plans involved directly harming and manipulating an individual in a way that none of the other team members did, which is another bonus- but even that wouldn’t seem so exceedingly evil if he didn’t have the unhinged maniac personality to go along with it and make him reject N outright upon his plot running into trouble.