Not like DM horror stories or anything, just the most traumatic experiences to your characters, or just really bad things that have happened that make you question everything.

For me it was really two times, and why I'll never be a player again in anyone's campaign. The first story is about my Lizardfolk Myr'yk a Kenku village was being burned by a series of light beams coming from a giant hovering gemstone shooting its light to smaller gemstones orbiting it. One small gemstone wasn't aligned properly and that beam was the one burning their village. I turned the light back up at the giant gemstone, and this set off a chain reaction creating a nuclear explosion.  My plan was that maybe this was the puzzle solution and by aiming the light at its source maybe it'll stall the light or stop it. Not nuke my character into radioactive dust and instantly kill my character because I rolled a Nat 1 on the Dex save. 

The second time was when I tried playing a loveable purple Grung that just wanted attention and love, her name was Needy and boy was she. She wanted hugs and to hold peoples hands. After the second time I tried to hug a party member, with the party member not even knowing that she is poisonous to touch, the DM let the players kill my char outright. This one is on me a bit, but it was a harmless poison, AND the players didn't even know about it yet. But dying like that basically twice in a row by two different DMs in two separate games put me off from being a player entirely.

I realize after writing this, it still turned into DM horror stories in a way, but please don't keep this trend XD I genuinely want to hear about in game occurrences.

got to say that the first one sounds like a dick DM decision, from a DM who didn't care about your character (putting a nuclear bomb on a hair trigger is going to result in bad feelings). Second sounds like you tried to play too roleplay-y a character in a game where the other characters were murderhobos.

Both of these can be easily avoided by having a session 0 - don't be so easily turned away!

For tragic stories, in the one-on-one campaign I am running for my fiancee;

the artificer who's acting as quest giver was a werewolf, and her son was born a werewolf. Her son was killed by an angry mob, and she converted herself to a warforged to escape the curse. She is now looking for a way to end the curse of lycanthropy.

Molly, the ranger and sole PC in the campain, started out by taking a group of people into a gnoll cave to wipe them out. One of them died, and it turns out he was the father figure of an NPC called Lam, who had really liked Molly but now is quiet and reserved around her.

Molly later had to kill some Owlbears which were terrorising a stretch of road. In a typical Cliche, she now has a baby owlbear called Sven, because the two owlbears she killed were his parents.

Then there's the times when we didn't finish a oneshot and we wrapped it up with a 5-minute summary at the end. those times are tragic.

I hear you, lol no session 0 was had so I tend to stay away from campaigns without them now, or would if I ever wanted to play a PC again.

oof the owlbear orphan T.T gets me every time.

More werewolf tragedy incoming:

Lycanthropy in my campaign is incurable. The barbarian was the world's first cured lycan, haunted by the evils in her past (player came up with this trauma, not me!). She didn't know how she was cured and why the emotional pain won't heal, so I eventually revealed that a cleric of the goddess of second chances channeled divinity to grant her a miracle, only the cleric had been a victim of the barb's rampage and harbored hatred in her heart, thus tarnishing the miracle. Eventually, the barb and cleric met and reconciled. It was a lovely moment of peace, and the barb even was chosen to wield a legendary divine blade of the goddess. Happily ever after, right? Well...

During the course of adventuring, a rival god of wit and power (coincidentally, the god rumored to have invented lycanthropy) came to the barbarian in a dream and spun her a tale of how lycanthropy was originally meant for good and had been corrupted. He offered her an opportunity to reclaim the pure wolf and said she would be able to control it. He offered it three times, just to make sure it's what she really wanted. The barbarian agreed. But the god lied. She's now more of a monster than she used to be. And because she refuses to accept responsibility for this decision she made, the goddess of second chances is now pissed at her for spurning the miracle and has cursed her legendary sword until she learns to appreciate second chances.

My stomach was in knots as the barbarian blindly walked into the god's trap. Moral of the story: insight checks are your friend. 

today I dmed Ten Candles...