HelloI was wondering if there is an already vanilla made trigger area that when the player enters gets instantly killed?

Unfortunately I don't think there is. A shame, because I know there one just such a thing in Oblivion.

*EDIT: You could make a normal trap trigger and set the trap to cast at the triggerRef (can't miss). If you use a custom super powerful spell, you wouldn't have to write your own script.

there is a kill player function?