Once upon a time a friend of mine from college asked me if I was interested in a homebrew campaign he was getting together. We had played together a few times before, once with him as DM for a one-shot and he had done a fantastic job. So I said yes.
 
He asked me to invite other friends as well. I invited some friends, but the only one who was interested was a guy we'll call Art. Art was a couple years older than me, going to college after just finishing a contract in the army. He had never played D&D before, but said it sounded like fun and he wanted to give it a try. He was really well built and into fitness as well as friendly, and knew how to have a good time. Art is the kind of guy who does everything 100%, so when he agreed to be a part of the campaign, he started reading through the player handbook and watching videos to learn everything he could about being a good player.
First session arrives, we meet at the DM's place and everyone introduces themselves. The other players are a friend of the DM, Bob and a friend of Bob's, Jenny. The DM obviously has eyes for Jen. I honestly wouldn't be surprised if that's the whole reason he invited Bob in the first place. The DM pays special attention to Jen and her pyromancer Sorcerer character. Completely neglecting Art who was brand new playing a human fighter. Of course.
 
As the sessions go on, the DM introduces several NPCs that all say creepy, edging on inappropriate things toward Jen. She politely turns them down each time. Meanwhile both in game and out, she starts to flirt with Art. After a while it's pretty obvious they are interested in each other which causes the DM to start targeting Art. He refuses to help whenever Art asks a question or anytime he attempts to do something cool. 
 
The enemies always seem to go after our fighter as well as get random buffs, but the party works together and Art doesn't die. At one point the DM flat-out told Jen that there's no way her character would be interested in Art because his charisma and intelligence were both really low. To this day I still remember the way she looked over at Art and then told the DM: "Well maybe my character just likes big strong dumb guys." That was the final straw.
 
The next session was a dungeon crawl and it was filled to the brim with traps and monsters. Of course most of the attacks and traps required either an Intelligence or Charisma saving throw. He repeatedly tried to get Art's character charmed, I'm guessing so he could either make him attack Jen or have him do something gross with one of the monsters while she watched. Finally we find the dungeon boss, who is some kind of homebrew buffed Succubus with a few minions. Near the end of the fight everyone is at their limit. Bob is making death saving throws, my cleric and Jen's sorcerer are both out of spell slots. Art has Guidance so he has made his Wisdom saving throws so far, but is one or two hits away from going down. Art has the sentinel feat, so thus far the Succubus has stayed out of his reach. After another failed charm attempt, the Succubus moves right in front of Art. Naturally, Art moves to roll some dice for his attack, but the DM stops him and says, "I only moved 29 feet, so I'm 6 feet away." Art gives him a look and asks "Are you sure you want to do this?" The DM pretends like he didn't say anything.
 
It's my turn next, then Art's. I'm completely fed up with the DM's antics, so I announce that my cleric will be dashing to move within five feet behind the enemy to flank it. Art goes next, says he's going to attack, and starts rolling dice. He gets enough to hit, then the DM says that his attack misses because he's still 6 feet away. Art is visibly angry by this point, but calmly says, "I take one step forward and make my second attack." He rolls twice and the second roll is a crit. He then action surges and makes two more attacks, both of them hitting. After adding up all the damage from various bonuses, the DM starts to get visibly teary-eyed, then says that everyone in five feet has to make a dexterity saving throw. I fail the save and my character takes a huge amount of force damage which not only knocks him out but instantly kills him due to massive damage rules. Art makes the save. He is out on the ground but the fight is over, because I guess Succubi randomly explode when they die. Jen's character immediately runs over and heals him with a potion. The DM told us that the session was over. I think there were some half-hearted goodbyes at that point, but everyone left pretty quickly and we all knew none of us were coming back.
Fortunately Art decided to give D&D another chance. He and Jen found another group to join and they still play together, the last I heard. I haven't spoken to my former friend the DM since then, so I have no idea what happened with him, but I hope he's grown and is doing okay these days.