Probably drugs, religious icons, bodily injuries, children getting hurt, alcohol and cigarettes.
Also strangulation, bullet wounds and broken glass.
It's also children being endangered, rather than hurt.
Story a friend used to tell when he was working on Ollie's Under-the-Bed Adventures, where the characters were trying to convince the local rich kid to help them or something. In the scene, he was on a lounge on his lawn, and when he refuses them the security goons throw them onto the sidewalk.
Well, one of the characters was a girl, and the animators were told they couldn't get away with having her thrown onto the sidewalk. So they had one guard push her while she dug in her heels, making furrows in the ground. Sent that to Legal, and word came back it was unacceptable. So they re-did the scene with a guard on either side lifting her by the arms, carrying her to the sidewalk and setting her down. Sent that to Legal, and word came back that the guards weren't allowed to touch her at all. So the final version of the scene had the goons walk up to her, and all three of them just walked off the lawn.
That's pretty much how things go in TV animation. The younger the audience aimed at, the more restrictive it is.