Depending on the chaos level, more dead bodies lay around in several locations.
The insect infested enemies are gorey and one can consider the disememberment of enemies to be gorey, but that's as far as gore goes.
There are suggestions in the Heart's comments that this may be the case for some of the witches. Delilah was treated badly (by her father and the world) and seeks revenge for it.
You can use sleep darts or chloroform to knock out NPCs. A character uses a serum which changes their personality, and does not remember doing so when not under the influence.
Several comments by the Heart indicate the deaths of NPCs' family members. When playing as Emily, the protagonist can optionally kill her mother's half-sister.
Crown Killer takes a serum that turns them evil, and doesn't remember it. Jindosh is referred to as lacking empathy, killing childhood pets, and removing the legs from beetles, a fairly stereotypical depiction of sociopathy/psycopathy.
Even on a Clean Hands run, it is not possible to prevent all deaths, only to avoid causing them, and it is easy for players to kill accidentally and have to reload.
No sharks. There are carnivorous fish called hagfish, which will attack the player character when swimming, and the game's version of whales have long, sharp teeth.
The nonlethal option for one target involves claiming they are their own body double. One character has taken a serum that turns them evil, and continues doing so without remembering. Guards and authority figures convince them that nothing is wrong and work to maintain their ignorance of their own actions.
Nothing explicitly shown on screen but a character describes how she faced physical abuse as a child after being falsely accused of breaking something.
A character uses a serum that changes their personality. There is a room in the palace with sleep darts, a syringe, chloroform, beds, and a dead civilian.
You can shoot fire bolts from your crossbow, or throw Molotov cocktails, which can set people on fire. Their bodies darken from the burns.
Also, bodies can be completely disintegrated with certain security features (walls of light, arc pylons, etc)
There are special kill animations where the player severs the limbs and/or head of an enemy. The player can also cause an enemy to explode, leaving behind bloody limbs.
Possession is one of the powers you have. You can possess rats, bugs, fish, dogs, and humans. With the right upgrade, you can even possess a dead human body.
Human corpses being used by bloodflies as nests are commonly seen, and have several holes bored into them like a wasp or bee's nest that may be reminiscent of trypophobia
When the player engages in combat, sounds of mutilation on flesh can be heard. When the player gets attacked by insects, a disturbing noise can be heard also.
[SPOILER]
This is the non-lethal method of eliminating one of the main antagonists. You strap them into a chair, and electrocute them, causing them to lose their intelligence.
A syringe is used to inject an antidote to cure an ailment one of the antagonists is suffering from, and is involved with the non-lethal elimination of that antagonist.
There is a level set in a mental institution-like building which is not currently open. However, it is not like a normal video game mental institution setting as it is closer to a luxury hospital for the rich and there are no inpatients while you are there. Anything scary in the level is not due to it being like a mental institution.
Crown Killer takes a serum that turns them evil, and doesn't remember it. Jindosh is referred to as lacking empathy, killing childhood pets, and removing the legs from beetles, a fairly stereotypical depiction of sociopathy/psycopathy.
The Crown Killer is the product of an experiment go wrong. The person experimented with a serum on themselves which led to a "split personality" of whom they have no memory of. This can obviously be read as DID misrepresentation, because of the violent "alter ego".
There are multiple LGBT characters in the game that can die or are dead by the start of the game. Two targets, Delilah and Breanna, are bisexual and a lesbian respectively and can be killed, though there are nonlethal means of taking them out. There are also LGBT characters you can optionally kill, such as a gay man named Aramis or a trans woman named Mindy. Aramis' lover, Theodanis, is dead by the start of the game but it is only vaguely referenced in game that he is dead and only hinted at that he even was gay.
Nothing explicit shown on screen but a character makes a comment about "this is better than any orgy I've been to" as a reaction to witnessing a magic ceremony. Also several times throughout the game guards can be overheard reciting a rather sexual limerick.
You earn the happy ending by killing as few people as possible, or none at all. Avoid detection, and use non-lethal takedowns whenever possible.
However, if you kill too many people, the game will enter "high chaos," and the ending will be bad.
If a NPC falls into the water, they instantly die. An NPC can be dropped or pushed into the water by the player, but they shouldn't ever fall in normally.