I've had 2 Guitarist from Hell experiences in the past year..
The first was when the band I was in at the time fired our lead guitarist; I was the new guy, and he had been in the band for 2 years, but despite that, I knew the songs better than he did, and he was the most inconsistent, undisciplined and crappy-toned guitarist I've ever encountered. Never played the same thing twice, didn't want to listen to any advice from the rest of us, or our requests for him to write parts that worked with the songs, and just got defensive all the time. They had been putting up with it all this time out of a sort of malaise, and when I showed up and started whipping things into shape a little bit, they realized how good these songs could be, and how much he was detracting from them.. he didn't want to shape up, so we had to be brutal with him and let him know that he wasn't in the band anymore. Anyway it seems he completely blamed me for the whole thing, despite the fact that I wasn't even the one who originally suggested firing him, and his parents (whose house we had been jamming in)also had a mean on for me after that. His father (who was clearly an alcoholic ex-musician who was living vicariously through his son) went so far as to accuse me and the other guitarist of stealing one of his crappy guitars (a Squier, as I recall), and called me repeatedly, threatening to call the cops, etc, if we didn't give it back. The guy we fired actually admitted to losing the guitar to his dad before this ever happened, and yet the guy still tried to get a guitar out of us.
The second time was last month, as we were trying out a new guitar player in the band I'm currently in. Very similar kind of guitarist to the one that was fired from my last band (the other guitar player from that band is in the current one as well).. he basically came in, started playing his own riffs, which were decent, nothing mind blowing, but not terrible. Problem was when we asked what he was playing so we could play along, he refused to tell us, claiming that he "doesn't know about all that note stuff - I couldn't tell you whether its an E or E flat or whatever, I just play what sounds right". Then he turned his back to me so that I couldn't see his fretboard, insisting that I should just play what sounded right. THEN when we were playing our tunes, he never bothered to ask for any insight or song structure.. nothing.. he just stood there making god-awful noises, both out of key and out of time with our songs.. and balked when we suggested he actually learn the established guitar parts. We finally had to tell him it wasn't working, trying to be polite, but he wasn't having any of it and started insulting songs that I had written and insulting my playing because I had said at the start that I wasn't a fabulous improviser, I prefer to take songs home to work on them (although, I added later, at least I can play along when given a song, unlike him). At that point I had had enough, and out came the brutal honesty. He left shortly afterward.
Having said that, though, the other guitarist that I've been in my last 3 bands with is an awesome guy, very humble and easy to work with, and a good guitarist, to boot.. so there is hope yet!