Is there any other kind unless the DM is actively seeking, planning to kill a PC? Characters die, it happens either because a player does something dumb, they get bad dice rolls, or they enter into a situation or combat that is above their abilities to survive. As a DM in certain circumstances if I inadvertently created an encounter that was way too hard for the players and I can come up with a logical reason to save a player's character I will, but I have never to my recollection ever set out to kill a player's character on purpose.
As the DM by nature of the game there's is always an element of DM vs the players. Not maliciously or out of spite but just because they are running everything else in the players world. They're supposed to challenge them, run their adversaries, even good and neutral NPCs. Take an NPC trying to hire the players to do a job, if the player's make too many demands, the NPC can just walk away. They aren't going to just roll over and give the player's whatever they want. The NPC is offering them "x" to do "y", take it or leave it, DM vs. the players in a manner of speaking.
As a DM it's my job to give the players exciting and challenging encounters, and make sure they have fun. I'm not just going to automatically say yes or no. I want encounters that the PCs can overcome but also have the chance to see them perish. I guess I'm impartial, I don't really care if they succeed or fail either way as long as I'm fair. If I was a player in a game with a killer DM, I'd quit, as I think most players would too.