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Besides considering what the other answers recommend (and, let's note that it's worth checking out similar questions - like, as Brian mentioned: "How do I deal with an experienced player who doesn't interact well with my group?" - and their answers as well), I'd say, there are two further options.

Note, though, that the best answer - in my opinion - is the one @BrianBallsunStanton gave here. I'm just offering a few alternatives to consider. :)

Besides considering what the other answers recommend (and, let's note that it's worth checking out similar questions - like, as Brian mentioned: "How do I deal with an experienced player who doesn't interact well with my group?" - and their answers as well), I'd say, there are two further options.

Note, though, that the best answer - in my opinion - is the one @BrianBallsunStanton gave here. I'm just offering a few alternatives to consider. :)

Edit: Let me emphasize that it is important to warn him of the consequences of the possible scenarios in advance both in-game and out of game, so that it doesn't feel like punishment is irrational, and comes deus-ex-machina, out of the blue. Let the group hear of Vader (or the 1000 years old troll) and his deeds first, in a tavern, from minor NPCs, etc. Show off the signposts, establish the rules of the world. When it comes to facing Vader, remind the player out-of-game whom he's about to cross. Also, remind the player of his actions possible consequences, notifying the others of their options, when he acts against his fellows: "If you steal their equipment, they won't be as effective when you come across the troll, and you might be worse off because of that. Also, if they ever find out you're the thief, they may kick your ass for it." Make it all just, for real.

Note, though, that the best answer - imo - is the one @BrianBallsunStanton gave here. I'm just offering a few alternatives to consider. :)

Let me emphasize that it is important to warn him of the consequences of the possible scenarios in advance both in-game and out of game, so that it doesn't feel like punishment is irrational, and comes deus-ex-machina, out of the blue. Let the group hear of Vader (or the 1000 years old troll) and his deeds first, in a tavern, from minor NPCs, etc. Show off the signposts, establish the rules of the world. When it comes to facing Vader, remind the player out-of-game whom he's about to cross. Also, remind the player of his actions possible consequences, notifying the others of their options, when he acts against his fellows: "If you steal their equipment, they won't be as effective when you come across the troll, and you might be worse off because of that. Also, if they ever find out you're the thief, they may kick your ass for it." Make it all just, for real.

Note, though, that the best answer - in my opinion - is the one @BrianBallsunStanton gave here. I'm just offering a few alternatives to consider. :)

Again, bosses have bosses who dislike their minions being one shotted.

Second, there's always the chance the the disgruntled other players will start a new game to which they won't invite him, only you. Or, sadly, that other group will only have time to play when the problem player is busy elsewhere, and the rest of the players will start having trouble keeping up with two parties, and consequently, start not being able to make it to this party. How unfortunate. (Yes, I've seen this happen in real life. A group has its methods of passive self defense.)

Again, bosses have meaner, more prepared, less "one-shottable" bosses who dislike their minions being one shotted (and have just learned how their minion was one-shotted, so that method definitely won't work against them.)

Second, there's always the chance that the disgruntled other players will start a new game to which they won't invite him, only you. Or, sadly, that other group will only have time to play when the problem player is busy elsewhere, and the rest of the players will start having trouble keeping up with two parties, and consequently, start not being able to make it to this party. How unfortunate. (Yes, I've seen this happen in real life. A group has its methods of passive self defense.)