Graphic: Death, Fire/Fire injury, Grief, War, Violence, and Suicide
Moderate: Stalking, Racism, Mental illness, Injury/Injury detail, Chronic illness, Murder, Death of parent, and Suicidal thoughts
Minor: Animal cruelty, Cannibalism, Torture, Slavery, Kidnapping, Fatphobia, Cursing, Animal death, and Body shaming
Death- Ghosts appear as part of the Paths of the Dead. Boromir, Gamling, Theoden, Denethor, Saruman, Grima, Otho and Lotho Sackville-Baggins
Grief- a major theme of the book.
War- while Tolkien is sparse in his descriptions of war and combat, he doesn't shy away from its nature.
Violence- a few one on one instances of various characters attacking each other, including
Suicide/Fire/Fire Injury- Denethor falls into despair and kills himself via immolation
Moderate- One or two references with more plot relevance/time spent beyond a passing reference
Stalking- Gollum stalks Frodo for several chapters
Racism- A reference to the Rohirrim hunting the men of the hill for sport, conflict and microaggression between Elves and Dwarves, the Orcs written as an Always Chaotic Evil race.
Mental illness- Eowyn and Theoden exhibit symptoms of depression, Frodo exhibits symptoms of PTSD after the Quest
Suicidal thoughts- Eowyn thinks of finding death in battle, Sam briefly considers ending his life when he thinks Frodo is dead, and resolves to come back to die with him when the Quest is over
Everything under "Minor" is an implication or something referenced once or twice in the text.
Animal Cruelty - Bill the Pony is clearly emaciated and over worked when the heroes buy him, but he survives until the end of the novel (despite first appearances) and becomes quite healthy and happy.
Animal Death- Bill the Pony is implied to have died, but survives. Snowmane the horse, however, does die, as do other horses used by the Nazgul.
Cannibalism- Gollum is implied to have once been a cannibal ("crept through windows to find cradles") and it is implied that Wormtongue killed and ate
Torture- Gollum was tortured when he was in Mordor, Frodo is whipped when he is in captivity
Slavery- The Dark Lord wishes to enslave all living things, and references are made to his slaves or servants every now and then.
Kidnapping- is nearly kidnapped by the Nazgul, but it's an incident recounted in passing
Fatphobia/Bodyshaming- Fredregar "Fatty" Bolger gets some snark from the other hobbits for being an exceptionally fat hobbit
Cursing- Frodo calls Sam an "ass" during a tense moment