No gore of the living person/mammal/bird kind. However there are bloated fish corpses that can explode, as well as mutilated animated zombie-like creatures in the base game. Grub creatures get decapitated and have graphic goo-spraying animations when they die.
If you play a Ranger and you have a canine pet, it can fight an enemy dog like it can fight other enemy creatures. Unless memory fails me, none of the times you can see dogs fighting is in the context of an organized dog fight however.
During lws4 a major character gets trapped in a robot suit with depleting oxygen supplies
In the icebrood saga the player character walks through a corridor filled with poisonous gas, with chocking sound effects when the condition first occurs.
Both players and NPCs can wield fire magic to kill others.
In Path of Fire, many characters die from fire.
Players can burn to death if they stand on environmental hazards.
The main character can fall unconscious multiple times, if your character is a sylvari during the first expansion heart of thorns you will experience faintness or dizziness, sometimes collapsing
No young children die, although many are threatened. Sylvari (who are born with adult bodies but the mind of a child) can die very young. Several adolescent characters die in the story, including one who is shot by their father.
Taimi is an orphan. If you are a charr, you have an option to kill your father. In Heart of Thorns, someone's mother is murdered. In LWS3, someone's father is killed, and it is revealed that (before the events of the game) he killed his wife too.
In Living World Season 4, a child is kidnapped and nearly killed. During the rescue mission, you can hear them crying and begging for help. Potentially very triggering.
There are frequent ghosts, but they are mostly a pretty silly kind of ghost. ghosts are basically just transparent people, who even have ghost weapons and ghost cannons. i'm not sure ghosts are ever used in a scary way
Ghosts can possess creatures and inanimate objects. During Heart of Thorns, an Elder Dragon can infiltrate some characters' thoughts, potentially completely corrupting them and turning them against their allies. A necromancer called Joko can revive people as his slaves; they keep their personalities but must obey him.
security forces are frequently shown as beneficial. especially if you are a human, as their stories focus a lot on the knights of their area, and show them exclusively in a good light
EDIT: End of Dragons does this even further, even featuring a police officer as a main character
There are several instances where characters are trapped underground due to cave-ins. In Living World Season 4, a character is trapped in a small space without oxygen, and you must free them. This can be a distressing scene, as you can hear the character suffocating and begging for help.
A section of Orr, Malchor's Leap, is named after a sculptor who killed himself by jumping off a building. Characters there will comment on the circumstances of his death.
Asura pride themselves on their intellect, and look down on anyone they deem less intelligent. Taimi, a child with a degenerative disease, is often mocked by her asuran peers. Some characters are belittled for their phobias. A charr war veteran in the Icebrood Saga is mocked by children. Some characters employ casually ableist terms in their dialogue, such as "stupid" and "lame".
There are several examples of fantasy racism. Many humans treat charr, centaurs and ogres as "savages", and try to have them imprisoned or killed. Many charr in their homeland are very xenophobic to visitors of other races. Many people express extreme distrust of sylvari once the jungle dragon awakens. Many asura pride themselves on their intellect, and treat people of other races as lesser because of this.