I may be getting some details wrong, but it is my understanding that
@EzekielRaiden has had some EXTREMELY bad experiences with DM's on power trips in the past, and they feel very strongly that DM's should include a conversation in Session 0 about what kind of behavior and actions should be expected from the Warlock's NPC Patron (if such a patron is being incorporated into the game - some GMs like myself being flexible, and others like
@Micah Sweet always including them). This conversation should include mention of any potential punitive measures the NPC Patron might take if the character does not agree to the Patrons requests during play.
This would then allow the player to make an informed decision to skedaddle or not.
I think
@EzekielRaiden also advocates for NO punitive measures from NPC Patrons that include such things as loss of character level abilities, penalties to their stats (that don't have saving throws), or being blocked from taking more levels of Warlock, etc. I don't know how they feel about non-mechanical cosmetic consequences like your limb looking like a withered husk, or the NPC Patron inflicting things on the environment around the character, like all plants withering to death. But I assume they are opposed?