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
Ren and Stimpy was already mentioned, and that one is pretty out there. Rocko’s Modern Life would be a trailing second place imo. Plenty of innuendos and inappropriate storylines in that cartoon.