Killer I guess, but only because I'm not a puppy love DM. If the dice say they're dead, they're dead; I don't exactly celebrate on making a kill, though.
To me, the game becomes far more exciting when the PCs are up against something that may very well kill them. If they somehow make it out of situation after situation where they should have died, they'll start feeling like it doesn't really matter what their actions are. A victorious fight where the PCs were left to their own devices to survive with no outside help will be far more satisfying. With that though comes the occasional death, but the players know it's not delilberate on my part, and besides, they're pretty good at staying alive.