This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / Grojband
In "Myme Disease", the town of Peaceville end up killing a man who was thought to be a statue.
The very fact that Peaceville has a maximum security prison....for Pre Schoolers.
In "Kon-Fusion", Trina is disappointed that Grojband fusing with the Newmans didn't kill them.
In "The Bandidate", Grojband protests against the corrupt mayor Trina, and the town stands up to their 'super-cute' leader. At one point, a lady holds up a rope implying they wanted to hang her...fourtunately, she gets pelted with garbage.
"Hologroj" : Thanks to confusion from the holograms and Mina's philosophy book, Trina slowly loses her sanity and thinks nothing is real. She turns to the fact that at least Nick Mallory can't be fake, but is once again tricked into thinking even he, too, does not exist. The last we see of her in this episode is her 'diary' sequence, and after this, we never find out what happened to Trina - or at least her grasp of reality.
Not even Grojband's presumed deaths net them much fame - the episode ends with Peaceville believing they're actually dead and that the real Grojband is just a cover band.
In "Dueling Buttons", Corey loses his cool after seeing Trina become famous because of a video game. If he didn't compose himself, he would have ended up somewhere in "Angry Diary Mode" territory.
Another instance is Corey's monologue in "Girl Fest".
One episode ends with the entire city destroyed by a flood. We can only assume thousands of people died even worse, Trina (Of all people) drifting in the water, discovers the evil brainwashing device that caused the flood in the first place.
The Time Travel episode, has Trina smash the time machine controls, while the gang was mid-teleporting. With complete intent to "Get rid of my dorky brother and his stupid friends once and for all" though while all it did was send them a year into the future, it could have easily sent them to the void for all eternity sure, Trina is evil. But this is low even for her.