To all who want to complain and bitch about the way 'DEAD' was treated, mabey you just like a simple hack and slash!!! Keep playing your simple games and leave the best Dms' to do their jobs. And thats kepping the players guessing.
Well, I wouln't call my game hack and slash, but it is a little heavy on combat.

Of course, I run combat heavy stories/adventures.
I like to mess with player's heads in one of two ways:
1. Play Paranoia

2. Use cursed magic items.
For number 1 I like a clasic game with some straight thrown in for good measuer. For number two, I like to keep cursed magic items to a bear minimum, so the players get lulled into a false sense of security.
Your biggest mistake wasn't, as far as I can tell, changing the PCs alignment, it was doing it without style. The idea, as it states in my new holy book (Paranoia XP) on page 94, "Don't torture the players--just mess with their minds." Really, if you're going to mess with a Player Character on that kind of level you have to do in such a way that the Player enjoys it. Yes, the DM needs to enjoy the game too, but the DM needs to enjoy the game with the players, not at the expense of the players.
I once had a dungeon where, in an earlier encounter, the party had fought a rust monster. Instead of leting the monk handle it, the heavly armed (and armored) fighter and barbarian pushed their way up front (they knew it was a rust monster) and fought it themselves. Well, wouldn't you know it, the rust monster got both their armor and their weapons. They were able to make due with some back-up weapons and some armor they found in the dungeon, but it wasn't as good as the ones they lost.
Untill they fought the Frost Dragon. After that fight, the fighter picked-up an adamanium breastplate that was much better than the armor he lost to the rust monster. He put it on, and it molded to his body. Remembering that magic items often, if not always, re-sized themselves, he thought nothing of it.
Then he couldn't get it off. Well, not to worry, he'll handle it later. Well, later came and he was going into his first major combat wearing his new armor and, wouldn't you know it, it turned him invisible. Hey, maybe this armor is a keeper after all!
Then it started, in the middle of combat, shouting "death to all chaotic creatures!" and directing him to kill certian creatures first. Then it started to win arguments. Not good. So He tried to get it off really hard this time. No good, it was glued to his body with sovereign glue. He got it taken off a couple of sessions later by gnome wizard's aprentice who couldn't find any universal solovent so had to do it the hard way with an antimagic field and a crowbar. It delt some tempary constitution damage and he had a nasty scab on his body from loosing a few layers of his skin.
Through all of this, he had complete control of his character. He got to play the reactions, the horror, the pain. He remembers that and it's talked about more than the battle with the Frost Dragon that gave him the armor in the first place. He had if for a few sessions, but only last couple or so was it a problem.
Oh, and if he had complained to me about it or posted a message about it here saying he felt it was wrong, I would have talked it over with him and found an even quicker solution than the one I used.
Style, use it or lose it.