One that was dark in a way but struck me funny as heck, was when my Vampire Hugo Villareal caught his brother Max (they were both adults and both vampires by then) with Hug's wife, at Club Nosferatu. Hugo went into an Enraged state, and went around the club Drinking Uncontrollably, all the humans! He was flitting from victim to victim in bat form, so I could barely keep up with him with the cursor, and he was filling up the club with urns and crying people! Note I was using mods for autonomous actions, realistic reactions to things like cheating, and also to enable death from drinking uncontrollably, as a vampire.
More recently, in a story I'm doing called The Legend of Forgotten Hollow (over at Archive Of Our Own now), a vampire who was a real piece of work, got parched, and while I was busy with other Sims trying to get screenshots for my story progression, darned if he didn't suddenly and autonomously attack Vlad's butler and Drink Uncontrollably! The two were pretty much enemies, but Vlad and his butler were romantically attached to one another, and Vlad flew into a passion and staked the vampire!
The thing that happened next was pretty astounding and I think a glitch of some sort: Talon (the vamp who attacked the butler) could not die, he just went into agonies of little embers flying up off of him, a big horrid chest wound, and Vlad covered in backspray. Caleb was there too and kicked Talon in the tenders for something he did to another character,
And I could not figure out why Talon could not seem to die! In fact right before Caleb kicked him, he was defiant in Caleb's face while burning!
So I did some things to remove some things that may have been interrupting the death process, tried an interaction called Suck Out Soul and THAT was dark, lemme tell ya! Really amazing visuals though! Talon's body levitating and draping from the waist, the worst facial expression ever, while ghostly forms and skull-like mists poured forth from him! Pretty epic. But then when that part was done, his body fell to the ground with eyes rolled back and mouth wide open, disturbingly corpse-like, and now his back arched and he went rigid and started shaking and making the worst sounds ever.
The other Sims were overcome with horror at what they were seeing and when Grim finally came, I was even wishing he'd hurry up and end it! And then when he stopped fiddling with his device and finally did the deed, it was so cool with huge blue flames and such!
So it was very dark, but very much an impressive and interesting spectacle.