How do I kill Brynjolf?

In the quest "Blindsighted" - right after the player and Brynjolf become Nightingales - I had to use cheats to make it work. After that I had Brynjolf following me everywhere.

I've tried killing him, but he just keeps reviving himself, and now he is trying to kill me over and over. I've tried setting him to be mortal but it wont work! How can I kill Brynjolf and be done with this?

Solution 1:

You can't kill Brynjolf, he is marked as essential throughout the entirety of the game. Also you do not need to kill Brynjolf ever. Also he is supposed to follow you to complete the quest "blindsighted".

The person you kill in "blindsighted" is:

Mercer Frey

To get rid of Brynjolf, you need to complete the quests so he will stop following you.