I feel your pain. I have a brother who makes...suboptimal choices whilst gaming as well as in real life. One memorable incident had him (well, his drow rogue) thrown down the stairs to a hydra due to annoying the other players by (for instance) killing the NPC cleric sent along so the group would have a healer. (This tale is only slightly dampened by the fact that the others didn't know the hydra was down there.)
The biggest problem? He tried to argue that his pet bird grabbed his rapier and killed the hydra somehow.
His next character? Tried to kill the kobold wizard that the rest of the group was talking to.
...Yeah. Not quite as bad as your brother, but then again I've never tried much in the way of curses. In the aforedescribed campaign, he complained for sessions (not constantly) about a pair of gloves he thought were Gloves of Dexterity but which turned out to be cursed.
Back to you.
If you can, just don't let him play. You can say that running the adventure with this many players is a bit taxing on you, and ask for the players to vote on who leaves.
If you can't, here's my two cents.
Talk to him and explain why what he is doing is making the game less fun for everyone. The other players' experiences are suffering? You have an excellent arrow in your quiver: The fact that you're not the only person who finds his antics irritating. Does this help you any?
If that fails, next time he makes a "new" character, go over his character bit by bit. Point to each number and definition, and explain what it means. "'Barbarian' means you have little education and can channel your anger in combat. 'Int 15' means you're basically a genius. 'Wis 13' means you're a bit more insightful than normal..." If he causes issues, you can point to the bits of his character sheet which explain why his character probably wouldn't do that, and ask if he wants to reconsider.
When all else fails, if he tries to do something absolutely idiotic, just act as if he didn't say anything for that sentence.
And if that, too, fails, simply don't let him come near enough to your games to touch a rulebook with a standard-issue 10-foot pole.
A more short-term bit of advice is simple: Have the game work realistically. You die? Make a character who could logically be wherever the other PCs are (say, in the Underdark, a fled slave of the drow) or wait until the group gets back to town. You attack someone? You get chucked in jail for years to life and the other PCs are likely to abandon your trollish hindquarters. Activate a trap? You get killed by the trap. Try to minimize the amount that these punishments affect the other PCs. For instance, that time with the Emperor? You shouldn't have had the party thrown into prison, you should have had a guard state his condolences for the PCs having to put up with that idiot...or just had the offensive idiot killed.