My Rogue/Shadow Monk (5e) had learned most of her skills from her older brother, who vanished inexplicably, leaving her to fend for herself in the slums of the cold, northern city where she spent most of her life.
After joining the party for a few years, we are drawn in to a chase with an insidious cult that have plans to retrieve an artifact and use it to open rifts in to other planes - to what exact end we are uncertain of, but we naturally go to stop it.
The cult had employed an assassin's guild to stalk us, gather information about us and kill us if the chance presented itself. However, they never made a move. For some reason, whenever we realised they were present, they didn't attack.
That was until we were close to catching the cult at the last stand near where they planned to open the portal (which was in an abandoned shipyard, now set ablaze during our pursuit), when a large group of the assassins appeared and stood in our way, with my Rogue's brother standing at the centre, clearly a figurehead. He had been preventing the entire guild from making any moves on us in order to protect me. He had been totally brainwashed by the cult and had gone off the deep end - he didn't even consider for a moment how I had felt after he just vanished to join the cult, just that he wanted me back.
I didn't think for a second before shadowstepping to him, getting a lucky roll to knock him off the platform with me in to an empty ship, demanding that our Sorcerer box us in.
The group was now fighting the guild while I was 1v1ing my brother, though rather than try to kill him, I was intent on beating some sense in to him. Our turns in combat were mostly loud arguing back and forth between punches and small nicks from daggers. Eventually, I manage to get the upper hand and disarm him, dagger at his throat. He just demands that I kill him, totally lost in his zealotry. When I refused, he ran his own neck across the dagger, killing himself.
The final showdown with the cult's leader became a lot more personal after that.