Honestly, the only con I haven't liked was Furlandia---but, in their defense, when I went, it was their first year. It was just very small, so there was little to do, and very few people to talk to, and there was a lonely dude who got overly-attached to me who was hard to shake *because* the con was small and there were so few people.
I find I either have a great time at AC, or just a so-so time. It's a matter of managing my expectations and goals, I think, as well as my energy.
I enjoy DenFur quite a bit, aside from the current convention space being a pain to navigate.
I've also historically loved BLFC, and I miss GLFC, because its small size allowed me to attend panels I might've normally missed, and have really nice, leisurely extended conversations with folks.
Rainfurrest, paws down. A few attendees wearing messed diapers in the lobby, drugs and damage found in many of the rooms that were trashed, and a used diaper left on the hood of someone's car all but cements this as not only the WORST, but it also damaged the fandom and was highly publicized.
The organizer, Nitrofox, basically made the furry equivalent of the infamous Fyre festival. I heard he was grossly inexperienced, stole funds meant to go to charities to cover costs, and mishandled the event at nearly every possible turn. Then, he lied publicly several times about theft of the funds meant for said charity, provided verifiably shopped receipts, and then deactivated his account when he was called out. Out of every Guest of Honor there, only one was paid anything for their time despite having multiple obligations and every one being expected to run a panel. To add to that, anyone just walking by could be a GOH because several shady people were walking the floor selling GOH badges.... Even the former admins of CCFC speak of the sheer incompetence and negligence, and many theorize Nitro was trying to impress Uncle Kage.
I hope this gives you a general idea, but I may have missed some details.