I would have to say (in no particular order)
- Grim Adventures of Billy and Mandy+ Grimm & Evil
- Angela Anaconda
- Fairly Odd Parents
- Brak Show
- Ripping Friends
- Whats with Andy
- Mega Babies
- Quads!
- Clone High
Check out list
- Happy Tree Friends
I love them all but its like, how did this shit get on TV and then anywhere near children lmao. Thank god they found their respective ways to us.
Edit: if its only one, try to post a thumbnail image so people can either try to recognize it or know if the animation style is for them
Courage deserves the lead
https://tenor.com/en-GB/view/courage-jumpscare-violin-girl-from-courage-creepy-violin-girl-jumpscare-gif-14348785
Ren&Stimpy had some gruesome stuff. Courage was more on the horror side.