as of november 2021, a scene where a child's dog is killed hasn't been animated yet. iirc that scene was removed in the volume version in case anyone reading this plans on buying physical copies.
Ep 1+2 of Season 4, characters are buried inside coffins while unconscious and held for ransom. They escape, you don't see them struggling inside or anything
noses/ears being cut off are mentioned as a traditional punishment- it happens once on-screen (though not shown in detail), and another character is disfigured due to this happening to him in the past.
At the start of season 1 a character is kept tied to a chair and has dango skewers stabbed through his cheeks. You mostly see the aftermath, the character is stoic, and he gets revenge.
A character gets an arrow shot into their eyeball (shown on screen). Another character pulls it out and sucks the poison out of his eyesocket (not shown on-screen)
a character who has multiple missing limbs struggles with several addictions. both of these things are often played for laughs (example: a character hiding their prosthetic arm from them)
There is a character who is consistently sexualized - groped by others, has nearly naked pictures taken of him in revealing positions, constantly the butt of sexual jokes.
A character's backstory includes a mother who seems to have a condition in which she repeats actions. It is unclear whether it is related to memory or compulsive, but it is in response to trauma.