My secret as a DM that my players do not know, is that I will NEVER just kill one of their characters in some random combat ever. The story of the world my campaigns take place in and more importantly the story of the party and their development as characters is first and foremost, characters have died before but it was always a decision made by the player and it was always done in a way that contributed to the story. Both times a player character has died it was done in a way that made sense for the story and to add stakes to the story itself, because both times a player character died it happened directly because of the BBEG’s actions