I'm still rather new to DMing and play with a group that's rather new to playing. 2 parents, their son and his friend. The kids are about 14. The parents haven't died at all. The kids have each rotated through a few characters. I killed one kid last session because it's what would happen. They came upon a battle. He decided to go off and saw a large hobgoblin giving orders to a little goblin. The player, a ninja, decided to shoot him with his bow. He took him by surprise, so the hobgoblin used his bow. The ninja was dropped to a couple of hit points. He then decided to move up. He moved closer to the big bad guy! Thwip. No hit. The bad guy just smiled and walked forward, pulled out a little throwing axe and chucked it at him. The ninja was in the negatives. The Favored Soul tried to get to him, and he did rather quickly, but the bad guy just coup de graced him. He used a ninja that he had made weak and tried to solo a powerful boss. It was stupid. I even told him that I was being nice in what I was doing having him slowly walk up. The worst thing that the ninja could have done was start moving closer to the hobgoblin. In situations like this, I have no problem killing characters. I do it often. If you're stupid, you deserve it. The new character isn't usually of a lower level, though. My group's not very good as it is. Weaker characters would not be a good thing. Mind you, I gave them a 36 point buy this time instead of rolling. Their characters aren't as powerful as they're use to.
Characters I've killed with this group in the last campaign and this new one: Shifter Ranger, Warforged Barbarian, Changeling Ninja. That might actually be it. Some of them I could have done a little differently, but I don't roll behind a screen, so they know exactly what happens.
I do like the idea of Revivify and using action points. I'll have to look up Revivify. As we play Eberron, I already use action points.