The main antagonist got the 'you are Alive when they start to eat you' death. At least her troubles were over quickly.
Hmm, memory's admitedly fuzzy on his death, but I recall it coming across as a major step down from the lady's. So much focus is given to hers' and she's even toyed with before ultimately being devoured, adding to the sadism.
Classic cartoons had this from time to time. A well known instance in Tom and Jerry is Tom's sudden beheading at the end of the Musketeers short. Just doing his job, Jerry and Tuffy caused this, and even after witnessing the beheading in question, conclude that war is like that and go along on their merry way. I mean, that could be excellent dark humor depending on who you ask (I myself admire the guts it took to go there), but it's undeniable cruel and out of nowhere. Then you had the Gene Deith shorts with Tom's male owner who would beat the shit out of him for kicks, including a short that ends with Tom tied up while and crying as fish are tossed at his face. And it's supposed to be funny!
The Donald Duck short Bee at the Beach comes to mind too. Don (inadvertedly) steps on a bee while setting up his spot at the beach. This enrages the bee who then throws sand at Donald's face (from Don's perspective this is the bee starting the conflict). Don then traps it in a soda bottle and goes for the sea. The rest of the short is the bee taking an unusually sadistic delight in pushing Donald further into the sea and do all in its power to have him eaten by sharks. It ends with Donald furiously trying not to be eaten by a bunch of them while getting more and more stranded in the sea, the bee observing this from the lifeguard's post (who of course isn't present), and finding it hilarious.
(There's something kind of fascinating about how many Donald shorts set out to utterly fuck the character we're predisposed to root for. The director for many of these confessed to growing to hate the character over time.)
Then you have that infamous Hey Arnold episode where Arnold's forced to parade in front of a laughing neighborhood, his Grandpa included, dressed in a bunny costume, and being clearly miserable about it. That episode was fucked up on its own but when looked within the context of a series that was idealistic and optimistic 95% of the time it feels like a mistake.