Double Dragon (1991): The moment Nightfall crosses paths with the Lee brothers who reunited with their father, he wastes no time revealing the And I Must Scream fate he encased the brothers' deceased mother in and relishes in every second of it.
The Decepticon Justice Division consists, as far as anyone can tell, of four people who take a sick pleasure in viciously murdering people, and one guy who swears that he doesn't take a sick pleasure in viciously murdering people, but is still doing it and conducting performance reviews to encourage the other four to be the most effective vicious murderers they can be. Oh, and Nickel. She's their medic. And even in the DJD Tesarus is generally shown to go above and beyond when it comes to cruelty.
Getaway, as he starts to show off even more of his personality, turns out to be particularly petty, spiteful and cruel, taking pleasure in mocking people before he has them killed or choosing particularly miserable fates for them.
Trepan, in his brief appearance, is shown to take a certain joy in the thought of ripping out chunks of Megatron's mind. Notably, at this point in the timeline, Megatron hasn't done anything worse than 1) critique the Cybertronian orthodoxy and 2) write bad poetry.
