I had a paladin tiefling in my first campaign that was always bugging for a warhorse… After about a month of none stop pestering I finally give them the opportunity to get one. A few sessions later the player was complaining that they weren't as powerful as the other players, they were level 3 and the rest of the party was lvl 4 because they missed a few sessions, I told them that they would probably level up in a session or two, subsequently the party would be captured by a mindflaire and drow and would have to fight there way out of a dream world they were stuck in and two of the party members ultimately died in the process, the paladin and a firbolg trying to heal the paladin, all of this happening because the paladin left a threatened square to attack a different hobgoblin, after that before even attacking the other one they tried going back to the first one getting cut down in the process.. mind you they were fully aware of attack of opportunities and only went back because the healer was over there. the paladin immediately started complaining and said they shouldint have died and how unfair i was.. clearly annoyed they started saying how at least now they didn't need to waste there time anymore.. it's funny how they said it was a waste of time because the party had to convince me to DM in the first place seeing how i was a Pathfinder player and didn't want to DM D&D and paladin was one of the biggest advocates for me doing it. regardless I rolled with the punches because my girlfriend was playing as well and didn't want there friend to leave.. so i had there god give them a gesture of Grace and resurrect them so they would stay. This kinda stuff would happen frequently throughout and I kept giving in for the same reason as before.. the session before there last was a week before Halloween and it literally ended off with them getting there own island of people! The next session was the Halloween special and usually I make it a one off type where your actions don't usually have any real consequences and this time around was no different. The players were in a maze and had to solve puzzles to get out, when they were finally able to leave there were some people who still wanted to explore and the paladin decided to leave without them.. they jumped through the portal at the end of the maze without the rest of the party and we're stuck in a void world until there rest of the party left… This is something I planned for if it happened and lucky for the paladin the rest of the party found some treasure and felt satisfied enough to leave shortly after we left off with the rest of the party jumping through the portal and of course the paladin was upset they didn't get any of the treasure and couldn't do anything for the last 5 min.. I reminded them that this one off didn't have any weight in the actual campaign and it only made them more upset, threatening to leave again. I decided I could give them some form of blessings for there efforts and the little experience they would have gotten the paladin didn't like the blessing and started insulting my abilities as a DM, saying how I "never let them do what they want" and "I never give them anything useful"… again threatened to leave and I finally cracked and said fine! A few months later and the same campaign is still going on and the environment is much nicer, we even replace the paladin with two much more experienced players and the party couldn't be happier.