I'll do my best to remember, but there have been many.
Shackled City (DM): We quit before starting the 4th chapter of the hardcover. The players found it was getting too challenging. I overwhelmed them with details, and they used investigation and divination magic to unravel much of the plot, which left them too terrified to continue.
Council of Thieves (Player): We stopped after the second book. A pivotal character was killed in a meaningless combat and the DM was unable to continue the story.
Kingmaker (GM): We stopped after completing the third book. The 4th and 5th books looked weak and repetitive. The challenges ahead also looked unsurmountable and the players thought it would be impossible and wanted a restart.
Shattered Star (GM): We stopped a session or two into this one because a player's spouse died unexpectedly. The heavy tone, preponderance of undead seemed distasteful so we tried a more "light-hearted" campaign.
Legacy of Fire (GM): We stopped in the first book after the party got stomped in an arena (I think). It was too hard, and they wanted to quit.
Rise of the Runelords (GM): I started running this at my FLGS. The party got to the first dungeon, decided it was too difficult to try to enter it (I think they had to cross a bridge), so they turned back and returned to Sandpoint. End of campaign.
Mummy's Mask (GM): We played one session of this. Schedules didn't work out.
Hoard of the Dragon Queen (DM): I ran this at the FLGS after running years of 4e D&D Encounters and the D&D Next Playtest. I feel that there was a TPK around the midpoint of the book. We ultimately quit because the group wasn't consistent, and I think there were like 8 players on average, and it was exhausting.
Masks of Nyarlahotep (Keeper): We completed this one in about six months of biweekly play. It ended in a pyrrhic victory, but the world was saved at great personal cost. Ended up being one of the best campaigns I ever ran.
Out of the Abyss (DM): I've attempted to run this one twice. The first time, the group was captured by duergar in Gracklstugh (about a third into the book) and were killed in a bad escape attempt. The second group a couple years later were convinced they were in over their heads after Sloobludop (very early into the campaign) and were clearly not having fun. I let them escape the Underdark and ran homebrew for the rest of that campaign - which is currently on pause from the pandemic. (Those guys are great. Mostly new to role-playing. They are my friend's coworkers, and he asked me to come in and run a one-shot to show them what D&D is - and we've been playing close to 2 years.)
Storm King's Thunder (DM): Honestly, I stopped running this one a couple chapters in, because I thought it was terrible. I continued with a general giant-themed story and we played through to a climactic end.
Princes of the Apocalypse (DM): I've also attempted this one twice. The first time was running it piecemeal and skipping around with my college gaming buddies when we got together a few times a year. They focused on one elemental prince and did a dungeon related to that prince each time we'd get together over a period of a couple years. Ultimately there was an epic showdown with Imix - and it was amazing. The other time I tried to run this I was running it with my girlfriend and her family, including her dad who had gotten her into the hobby when she was younger. He hadn't played D&D in probably 15 years, and it was awesome. Then I killed her family with a random encounter with gnolls. And we broke up soon afterwards - so that game ended.
Tomb of Annihilation (DM): I ran this one to its conclusion. A big, epic fight at the end of the dungeon. We had a good campaign, even if I ended up glossing over the jungle exploration after a few months of real time of nothing but random encounters.
The King in Yellow (Keeper): The group's second foray into Cthulhu didn't go so well. Early in the book they had a TPK to a group of ghouls. Apparently, they thought they were playing D&D. We decided to stop Cthulhu and try out WFRPG (see below).
Enemy Within (GM): We had a couple good sessions in the first book, Enemy in Shadows. After completing the second chapter, one of the players had to relocate for work. That left only three players, and they wanted to try out PF2 (see below).
Dungeon of the Mad Mage (DM): My college gaming buddies who finished PotA wanted to have a fun, old-school dungeon to play online since our occasional gaming weekends were getting harder to schedule. Over a month of weekly play, the dungeon was clearly not doing the trick. They had explored about half of the first level, which was mostly empty, uninspired, and didn't provide the fun experience they were wanting, so we switched to an adventure from Yawning Portal and enjoyed it more.
Dragon Heist (DM): Tired of dungeons for a bit, the college buddies wanted a city module. I had reservations about it due to the bad reviews, but they wanted to play it anyway. We did finish it, even if they completely bypassed a lot of the encounters, the chase scene, etc., because they had good rolls, played intelligently, and figured out everything quickly. The vault can be a textbook definition of anti-climactic.
Curse of Strahd (DM): Completed this one. The same group of players who ran away from Out of the Abyss, realizing we weren't getting back to that in-person game anytime soon wanted to try Curse of Strahd. We finished this one in about 6 months of weekly play. After some OSR gaming, they're now trying Frostmaiden (see below).
Age of Ashes (GM): The group that went from Cthulhu to WFRPG is something of an experimental group, always wanting to test out new rules sets. We started Age of Ashes in person then shifted to Roll20 during the pandemic. We completed the second book before ending the game due to the difficulty of the campaign, and interpersonal relationships.
Barrowmaze (DM): I've been running this as a casual weekly drop-in game for 2-3 months for my wife and her brother. They are having a good time, but we're only in the first level of the dungeon (which is massive).
Rime of the Frostmaiden (DM): Had our first actual play session last night with the OotA/CoS group. Very nearly was a TPK in the first encounter, but still going strong at this time.
Whew. That's a lot of games. So my current games are
1 College buddies, where I'm currently a player for a change in an Old School Essentials game of Caverns of Thracia.
2 My wife and in-laws playing Barrowmaze in 5e.
3 My friend's co-workers, just starting Frostmaiden in 5e.
4 Starting Abomination Vaults in PF2 for some folks I met on here just to see if PF2 can be salvaged from our bad experiences.
