In two super editions, tallstars revenge and crookedstar promise, the leads are abandoned by one or both of their parents (sometimes unintentionally but still)
It is a mojor plot point in both, more so crookedstars
I would argue that Ashfur or the Imposter displayed stalking behavior. He was obsessed with her alive and eventually became violent when she chose to be with another, and after death came back from the afterlife to possess the body of her romantic partner.
Turtle Tail and Bumble are both in abusive relationships with Tom in Thunder Rising. The Imposter emotionally and eventually physically abuses Squirrelflight in The Silent Thaw. Bramblestar gaslights and emotionally manipulates Squirrelflight throughout Squirrelflight’s Hope. Crowfeather and Nightcloud get into a physical altercation in Fading Echoes.
Violetkit/paw is neglected by her foster mother (Thunder and Shadow). Brokenkit is neglected and abused by his foster mother and bullied by his foster siblings. Stormkit, renamed Crookedkit, is rejected by his mother after breaking and disfiguring his jaw (Crookedstar's Promise). Thunder is rejected by his father, Clear Sky, as a child after losing his mother and siblings (The Sun Trail). Spottedleaf’s Heart focuses on CSA (child sexual abuse) between Thistleclaw, a grown adult, and Spottedpaw, a child younger than Thistleclaw’s son.
An often-overlooked scene (I forget which book it's in, I'm sorry), is where a cat asks for catmint (catnip) ((weed)), which in the book is a herb used for treatment of sickness, despite not being sick. It's laughed off and it's very short.
No but the book series can sort of act as propaganda towards letting cats outside to hunt, often phrasing the inside (kittypet) life as boring, bland or restrictive. Real life cats should not be let outside unattended (unless they are farm or working animals or are part of local stray cat colonies) because they can be injured or stolen, breed with other cats if not fixed and also majorly contribute to animals’ population decline and even extinction of entire species. Some countries have laws against letting cats outside due to them overhunting local animals. Please remember this book is fiction and don’t feel pressured to let your cats outside or feel bad for them being “trapped” inside, I promise they have a safer and better life inside than outside.
Honeyfern gets bitten by a snake and dies, along with Frecklewish (but this wasn't really an accident like Honeyfern's, rather another cat beckons a snake to kill her)
Bugs are mentioned plenty of times, i.e the phrase "bees in your brain", apprentices having to rid the elders of fleas, the Bee-, Fly-, and Beetle- prefixes, and probably more that don't come to mind rn
That one guy clearly didn't read Spottedleaf's Heart.
Anyone with reading comprehension or experience with the subject (I'm lucky only having the former) can tell that Thistleclaw, a cat with a son who is older than Spottedpaw, was manipulating and grooming her throughout the entire book. Unfortunately, it's never explicitly stated that what he did to her was wrong and not okay, which could lead to some young readers mistaking this as normal behavior.
In Spottedleaf's Heart, a super edition (and book neglected by most of the fandom) it shows a slightly disturbing relationship between an adult and child, and although nothing actually happens, the adult does try his best to get into a relationship with the child although fails.
Several cats die in a forest fire during Rising Storm, though at least some died of smoke inhalation rather than burning. In Long Shadows, a character tries to trap several other characters in a fire, but lets them live. In The Last Hope, a scene is written confusingly enough that it seems like a burning tree kills a character, though the character in question actually dies of injuries previously sustained in battle. In Thunder Rising, a character is badly burned during a forest fire and eventually dies of his injuries.
In Tallstar's Revenge, Talltail's father, Sandgorse and Leafshine, who died before the story begins die to a tunnel collapsing. It's also hinted that this happened various times before which led to the closure of the tunnels.
Cinderpelt, Cinderheart, and Jagged Peak all suffer broken legs (Fire and Ice, Outcast, and The Sun Trail, respectively). Crookedstar breaks his jaw as a young child (Crookedstar’s Promise). Briarlight and Frog suffer broken spines (Fading Echoes and Path of Stars, respectively). Clear Sky breaks his tail in three places in Path of Stars. Finleap’s tail breaks so badly in Darkest Night that it has to be amputated. Snowbush dies from an infected broken leg in Darkest Night. Snowbird breaks her paw in The Silent Thaw.
Darktail’s cult (The Kin) tortures Needletail by what is essentially waterboarding after starving her for days. Clear Sky starves Jackdaw’s Cry while holding him hostage in The First Battle.
Brightpaw is attacked by dogs and her face is mutilated. She loses an eye and part of her ear, but she lives. Longtail goes blind after a rabbit scratched his eyes, but he is alright and retires early. Brokenstar is blinded by another cat as punishment for the atrocities he committed throughout his time as leader.
While the other comment mentioned Snowkit I'll mention other young cats who have died. -big spoilers- Mosskit- dies due to exposure Sweetpaw- dies of food poisoning. Tiny Branch- dies due to blood loss after a fox bite. Mintkit and Marigoldkit- die due to early training (not a fox, as stated in Yellowfang's Secret.) Willowkit and Minnowkit- die due to greencough Morning Whisker- dies of sickness Tadpole- drowns in a flood
Feathertail sacrifices herself to save Crowpaw
Bristlefrost sacrifices herself to save Shadowsight
Needletail sacrifices herself to save violetpaw
Appledusk sacrifices himself to save Reedshine
Bluestar sacrifices herself to save Fireheart/and her clan
Appledusk cheats on Reedshine by having an affair with Mapleshade (Mapleshade's Vengeance). It is implied that Stormtail cheats on Moonflower with Dappletail (Bluestar's Prophecy). Brightheart suspects that Cloudtail cheats on her with Daisy, though this is later proven false (Twilight).
In the Forest there is a river that runs through the territories, and in the second series they move to a Lake which is where the rest of the Warrior Cats takes place
Police don't exist since these are cats, but the warrior code which is basically kitty cat laws are often enforced (TBC revolves around the code and codebreaking), even if they are unjust.
The word cancer" may not be used in-text, but a minor character in the prequel SEs, Tawnyspots, has "a lump in his belly" that slowly kills him, and the authors have stated out-of-universe that it was stomach cancer.
No self harm, but a cat does commit suicide by ingesting poison (not because he wants to end his life, but so he can find a ghost. he also comes back to life)
Also, another cat forces his followers to carve his symbol into their paw pads if that counts
In Mapleshade’s Vengeance, Mapleshade kills three cats and attempts to kill a pregnant queen, driven by hallucinations of her dead children. In Crookedstar’s Promise, a delusional Goosefeather chases Stormkit and Oakkit across the stepping stones, resulting in Stormkit slipping and breaking his jaw. Tigerstar experiences hallucinations and self-loathing throughout Tigerclaw’s Fury, although these hallucinations are revealed to actually be Mapleshade. Ashfur is implied to be mentally ill throughout The Broken Code, in which he is the main antagonist.
Cinderpelt/Cinderheart could be argued to be plural (haven’t read that bit yet but I’ll update this comment with my thoughts on if it’s misrepresentation or not soon)
Crowpaw in TNP attempts to kill himself via jumping out in front of a monster after Feathertail dies. He is saved by Brambleclaw and Squirrelpaw though, and yells at them for not letting him kill himself
Technically all the cats are being watched by Starclan, but there are a couple scenes where somebody is stalked or watched for a future plan. (Ex: Hollyleaf watching Ashfur unbeknownst to him to kill him later)
Bright Stream is carried off by an eagle while expecting kits in The Sun Trail. Several characters die in childbirth (namely, in Forest of Secrets, Crookedstar’s Promise, and Daisy’s Kin).
It is not intentional, but sometimes there are mistakes where a cat is called by the wrong gender, which are just simply things that slipped by the editors. This is worse for some cats than others.
Confirmed LGBT cats (Tallstar, Ravenpaw, ect) and cats commonly thought of to be LGBT (Redtail, Blackstar, Rowanstar, ect) die, as the books take place through several years. No characters are killed for being LGBT, many die from old age or natural causes; but some die in battle.
Eh, It's complicated. There's no racial or ethnic misrepresentation in Warriors, since these are cats. Although cats without Clans are often looked at with disdain by Clan cats, cats who think this are often shown to be in the wrong to do so. There's also no 100% canon LGBTQ+ cats in Warriors. There's no real world religions in Warriors, but sometimes Clan cats think that cats who don't believe in StarClan are weird. Many people in the Warriors fandom consider disabled people to be misrepresented in Warrior Cats.
Dustpelt and Ferncloud, Thistleclaw and Spottedleaf, Pinestar and Leopardfoot, Thornclaw and Blossomfall, Ivypool and Fernsong, Squirrelflight and Bramblestar/Ashfur, are some canon relationships with large age gaps that I personally find really bad or kinda weird
Religion is a very important topic in the society of the cats - they believe in StarClan, which is the equivalent of heaven. They also have an equivalent to hell. They have doctors / priests and leaders who have strong connections to cat heaven, and atheists are looked down upon. Many characters have dreams about or that take place in StarClan or the spirits of deceased cats. There's far too much to mention - the forest cats are very religious.
While it was an accident, two siblings end up becoming mates. There's also other accidents where two cousins will become mates, but it's never mentioned they're cousins or related at all.
No graphic depictions of strokes are in the series. Shadowsight has seizures, not strokes. Some cats (such as Sagewhisker) are confirmed outside the books to have died from cardiac events.
At some point in the "Dawn of the Clans" arc it's said that a pregnant woman who dies gave birth in StarClan (the equivalent to a Heaven). There are multiple instances where it is implied that the spirits of kittens who die while in the womb (despite their age) have full sentience in StarClan. While to my knowledge abortion is never even considered as an option in these books, there are many times where it is implied that if an unborn child dies in any way it will remember, and sometimes continue to age in the afterlife.
This being a book series, you can't actually HEAR anything, but I do remember a scene where a character is nearly hit by a car, and the sound of the car veering to avoid them is described. IIRC, the scene is built up to though, and isn't super important, so it can be skipped fairly easily.
While lots of characters suffer injuries with lots of blood, one specific death is very worthy of the gore warning in The Darkest Hour. If you want specifics of the injury (stop reading if not!), he is clawed throat to tail along his belly and loses all nine lives at once since the injury is so severe. There might be worse, but this is the first that comes to mind.