There's a difference between "games that are too lethal" and "games where combat is very lethal".
You can have either one independantly: it would be entirely possible to construct a lethal game with nerf combat rules (Ok, you slaughter the 10,000,000 orcs with your rusty dagger. Then you trip over a rock and die. Next character!).
It's the opposite that is interesting: you can have a game where combat is very lethal, but then combat is also easy to avoid. If you're in a stand-up fight, you've already made your mistakes. In such a game, the violent psychos tend to die out quickly, and as long as you don't stop the game to wait for people to roll up a new character, the people who insist on playing them won't get to do a lot.
Incidentally, recruiting the rest of the group as moral enforcers is probably the most effective measure:
My own shadowrun group, for instance, after having our missions ruined by a run of violent psychos with predispositions for revenge joining us told the next PC recruited "do what you're told on this first run, or we'll take care of you: no second chances, no excuses". The player decided that violent psycho was a great archetype, pulled a gun on our opening meeting with a client, and the rest of the party disarmed him, bound him, locked him in a car trunk and left him to cool his heels in a junkyard for a day.
Unfortunately we then left the country for a week and forgot about him.
But the point is: while we did enjoy playing combat (and by that point it wasn't all that deadly to be honest), we didn't enjoy having our goals wrecked by someone who wanted to indiscriminately murder or threaten random NPCs (or us for that matter). Violence had a time and a place, and that time and place were fairly obvious.