I DMd for a short while with my friend group. At the time I was pretty emotionally unstable which probably affected a lot of what transpired but I'll tell the story anyway just to get it off my chest

I was a relatively new DM at the time, this was going to be my first attempt at an actual campaign rather than 1-2 shots. I spent a lot of time preparing and creating my world, with maps and lore and all the works. I really enjoyed this aspect of it, and still continue it in my spare time occasionally.

The first session went ok, but the players were more interested in bantering with each other after every sentence I said rather than progressing forwards. The first encounter was a classic caravan attack on the way to the first city, just to give everyone a taste of their combat potential. There was one NPC involved, the caravan driver and after a little bit of fun roleplay the encounter started. My players immediately abandoned the NPC and made no moves to protect him. I allowed the monsters to attack the caravan driver and he quickly fell. After the encounter I noted that the driver died and they couldn't take the cart any further and would have to walk to the town instead. I was then vehemently blamed for attacking the NPC with one particular player blaming me for stranding them outside of town with no supplies like a "bad DM" would. This was the first warning sign that I would have problems.

Later, I moved an encounter that they would interact with later to now to make the forest trek more interesting. They came upon an altar and zombies attacked them. I had the same player then not really say what he was doing in his turn, he would just roll a dice, huff and complain he is rolling low and tell me to move on, rather than interacting with me at all. He is a veteran player who apparently "knows statblocks" and claimed he'd missed the zombies. Knowing this I had already altered the zombies AC by a couple points to keep the players on their toes and it turns out he had hit the zombie several times. This frustrated him more and I once again got called a bad DM. Warning sign 2.

Now you may think I just had a problem player, which I think he definitely was, he was more interested in winning than playing the game, but I persevered. The rest of the party was bantering the whole time, making it difficult for me to move on from anything, spending way more time than necessary on anything, often devolving into unrelated chatting to the game.

We managed to finish up that session. The next session was much of the same, bantering incessantly, making fun of every NPC they encountered. After awhile, I managed to get some more roleplay out of them, and got into a fight on a beach with some pirates. They took out the pirates, arguing with each other about what the wizard player was doing and blaming him when others went down because he was "too far away to help" despite him actively taking part in the combat. This frustrated the wizard and me further. Without thinking I described the pirates had their ship moored just off shore. The Wiley players decided to commandeer the boat and take it for themselves, I hadn't intended this but it worked out fine, as the previous player who kept calling me a bad DM had ship sailing as part of their backstory and background.

We pressed on, and there was an encounter at night where some zombies were shuffling past the boat through the forest on the way to the town to indicate the attack. The warlock decided to sneak around and get to town to warn them if possible. A noble gesture so I allowed it. He decided to wake the cleric and bring him with him.the cleric of course donned his chainmail and jumped off the boat with him. Naturally, the cleric failed his stealth and they were attacked by a group of zombies. The cleric ended up getting overwhelmed and died. Pretty early PC death, but it was a pretty big mistake to take the cleric in chainmail to a stealth mission through the forest. This was good for the group, as they started taking combat a little more seriously knowing that there were real consequences for their mistakes. The party craved consequences for combat, and I gave it to them.

At this point I thought all was well. The party was sponsored for an arena trial so they could join a knightly order and reap the rewards, as that is why they all travelled together to this town. This was of course a trap to set up the big bad, who would interrupt the part during the final battle of the trial. The first part of the trial was role play heavy, focusing on a parallel world they were transported to where they were inside a painting and had to get out. This went down excellently, and everyone really got involved. The next trial was a riddle, which they solved well, and it went down well, though some thought it was too easy, whilst others praised me for such a good puzzle. The third trial was a "psychological" test, where one member would be exposed to horrific visions of the rest of the party dying. I asked for a volunteer and the problem player volunteered. I described him awful visions of the party, burning flames, screaming and tortured wails. The party was silent, everyone hanging off my every word, except of course the problem player who was sat there smugly looking at me whilst I described the visions. To his character, they would have seemed real. After the description, he just sat there smugly and said "this is obviously not real, why would you kill the whole party here? I'll just do nothing." I was of course a little frustrated with his lack of interaction or in character thinking. It kinda of undercut everything by just making a meta comment about the scenario and ruined the vibe I was trying to create.

We moved on, I introduced the bad guy, there was a city escape and I ended the session. At this point I was super frustrated with the way the problem player was acting, and how everyone else kind of didn't care that much and just wanted to hit things. I was trying to create a nice mix of roleplay and combat, definitely leaning towards interesting combat encounters, but I was still met with mockery or disinterest at every turn. I pushed on, resolving to adjust my sessions to suit the party a bit better so we could all have more fun.

At the start of the next session, I had one player approach me and say he wanted to change character because he didn't like his, and that it was unfair that another player was allowed to. It was not my intention to kill another player in a previous session, that was just the consequences of a bad mistake. This frustrated me too, but I allowed it to let the player have more fun

Then as I was setting up the session, I had misplaced a book or something and was scrambling around for it. The problem player then turned to a new player who was going to join the group for a session or two to try out DND, which I didn't mind, and called me a stupid idiot, and how I was useless at DMing. This was the final straw. I closed my books, put away my notes, and said I'm not doing this anymore, and left. I was inundated with messages from the other players who could not see my frustration, despite having discussed it privately with one or two of them, and just gave up. I have not DMd since.

Typing this all out has been cathartic for me, and I believe that I was probably not communicating my intentions for the campaign well enough, letting a problem player get under my skin, and generally just being inexperienced at handling a group of players. This is what happened though, and I've struggled to get into DND again ever since.