Zero44 said:
... He says that D&D is 'boring' unless someone is there to cause trouble in the party and make them not live in perfect harmony, and 'screw up the 'perfectly-planned' plot". ...
OK, I have already said you should dump him. Normally, I advocate discussion, but your first post seemed to make it pretty clear to me that discussion wouldn't help. But, I will jump into the fray once again.
The player thinks that DnD is boring if he can't mess with people because everyone gets along too well. First of all, this is a relatively immature solution to the perceived problem. There are plenty of ways to have intra-party conflict without screwing over the other PC's. All it takes is Roleplaying.
Maybe the chaotic good character serves an important NPC a healthy dish of disrespect and gets tossed in the local lockup. The paladin (or any other lawful good character) may be incensed because the CG PC is making the group look bad, flouting authority, and being disrespectful to somebody he finds very worthy of respect. You can have wonderful arguments in character here, without ever having to steal or kill your fellow party members. Maybe both PC's get under each other's skin, but when the hammer drops, they both know that they can count on each other.
Maybe the Cleric and the Druid get into serious discussions on how people are overrunning the environment and engaging in deforestation. The Cleric views everything in a "human-o-centric" frame and the Druid is looking out for the forests. These two people might have difficulty agreeing on several things, but they also acknowledge that rampant Evil should be stopped. When things get grim, each can put aside their differences to take care of the problem.
These situations are perfectly valid RP that avoids the smiling-happy-people-holding-hands syndrome. If your player thinks he needs to play a diametrically oppossed alignment to make things "interesting", then he is not looking very far beyond alignments. There are plenty of ways that even like-minded people can disagree. Have you ever seen a LG Cleric and a Paladin, who worship the same god, disagree? I have and it is fun.
Maybe you can present this to the problem player in terms that he will understand. Heck, perhaps both of you like football, but cheer for different teams. You hang around with him because you watch football together and enjoy trying to prove why your team is better. But, you might not like hanging around with him if he only listened to opera and plotted ways to maim people. The fact is that he is creating characters that are not "interesting". His characers do not enhance the story, they destroy it. The rest of the PC's have no reason to travel with this PC, so why would they? His roleplaying maturity needs to progress to where he can make a teamplayer that has differences of opinion and somewhat different goals without having to be completely out of touch with the rest of the PC's.
I suppose the other problem might be if you run heavily railroaded plotlines. This could be a backlash against that. If that is the case, then the player needs to confront you with his feelings and tell you why he always feels constrained and railroaded. Perhaps there is something that can be changed with your DM style? If so, there are plenty of pointers to be had here.

Or maybe you just need to point out how the character decisions drive the story and if it seems too well harmoized, it is because the rest of the players are making a strong effort to work together and succeed - and he is trying to destroy that by making contradictory characters. (See above responses regarding what to do with a jerk.)
You seem determined to solve the problem with the player. If that is the case, then do so on the player level. Dragging it to in-game solutions is unlikely to work. I hope my near rant helps somehow.
