Owl, the player character Wolf's adopted father, is emotionally abusive towards Wolf, demanding absolute and unwavering loyalty and obedience. There is also a boss fight against him.
Player character will die a lot, main villain dies by suicide in one ending and decapitated in another, all three mentor characters are able to be fought as bosses, the closest thing to a love interest is also a potential boss fight, and the child can die.
A major character can succumb to illness by the end of the game. Also "Dragonrot" is stated to be terminal but no one ever actually dies from it in game.
Not slapped, but there are several female boss fights, probably the most triggering is the character Emma as a boss battle in the "Shura" or "Bad" ending route. Between her, the Okami, and Lady Butterfly, there is a lot of violence towards women, though never specifically because they are women. There's just a lot of violence in general.
No sharks, but there are giant, man eating carp with human like faces that will bite at the player character. Possibly triggering for people with shark-phobias.
The player character Wolf loses his left arm near the beginning of the game, it is replaced with a prosthetic that also serves as a secondary weapon. The animation of the current shinobi tool may feature the hand of the prosthetic separating or splitting apart in ways that could be triggering.
Not shown but it is relayed that a group of monks have kidnapped and experimented on numerous children, only one of the children have survived.
A child is also kidnapped and shown interacting with his captors at several points but he does not display acute distress at his situation.
During a cutscene a child is stabbed or cut off-screen and stumbles into frame. His survival depends on the player's actions.
Multiple bosses, both human and not, have giant centipedes crawl out of there heads/throats. Also the final boss though I won't spoil what happens, is particularly bad if that upsets you.
One character asks you to kill him but comes back to life as he is unable to die. He later asks you to kill him for real once you've discovered the means to do so.
One boss also cuts his own throat in a cutscene.