Now I Know Why They Call Them Clueless

Yeah, or imprisons one of their souls contractually in exchange for their freedom so he can use an abuse them at future dates that are convenient to the DM. If I killed my players every time they did something stupid, we would have deforested the Amazon for want of character sheets.

Yeah, I have a player who kills everything in sight that isn't explictly labeled "Good" in the Monster Manual... and THAT was in 2e and 3e, where quite a few creatures were of the "Good" variety. I expect him to be even MORE bloodthirsty in 4e, where there are maybe two monsters of "Good" alignment in the entire game! And I can pretty much forget having any recurring villians in the plot, since he kills anything that doesn't kill him first, thereby pre-empting any second encounters with the same foe... unless of course he dies first! To him, anybody he encounters is either there as 1) an ally to fight alongside, 2) there to give him treasure and/or info, or 3) there to be slaughtered for XP...

The simple fact that killing is obviously his only way to solve problems hardly qualifies this character as 'good' in my eyes...

>>2) there to give him treasure and/or info, or 3) there to be slaughtered for XP...<<

That is when you throw them against a villain who absolutely *wants* the PCs to kill him as the culmination of his ultimate plan, but discovering this in advance the characters have to avoid killing him - or letting him die in any way - at all costs.

Perhaps he hopes to free up his meat suit for a nigh indestructible possessing force. Or his death is the gate key to a plane of ultimate horror and destruction; the final sacrifice to renew a dead god; the culmination of a bargain with a devil which will grant his every terrible desire; the only way to get out of paying his Asimon ex-wife her child support; whathaveyou. It would be terribly amusing to watch the party's walking weed wacker try to keep a villain alive until X occurred and his plot fell apart. (must die within a specified period of days, for example)

Or stop giving xp for killing monsters, which is what I've basically done in games, but hand it out entirely for overcoming story based obstacles and finishing the adventure. (not necessarily by *defeating* it, though ... it is my opinion that so long as the group provides entertainment and attempts to rp, success or failure should have no impact on their xp reward - otherwise you're telling them the rpg is a game that has to be won, like monopoly)