Perhaps the most terrifying and shocking out-of-character moment comes from season 6, episode 12, “Waterworks”. Towards the end of the episode, after being spotted by Marion in a beautiful scene, Gene’s attitude suddenly changes, becoming a threatening one. Grabbing her phone cord and wrapping it around her arm in a creepy way, Jimmy/Saul/Gene is practically unrecognizable at this point.
Saul Goodman has always made his money at other people’s expense, but he’s hardly one to do the dirty work. There was hardly anything physically threatening to Jimmy, but now, with his identity and freedom, he suddenly had a sinister presence. The scene features him slowly approaching and talking to Marion as if he intends to harm her. At the end of the day, Jimmy doesn’t give in to his dark nature and instead runs away from it, revealed by Marion to be Saul Goodman.
However, the scene is a close call and shows the possibility that Saul Goodman’s character must go to an even darker level of crime, almost like Heisenberg.
https://www.slashfilm.com/968065/10-most-shocking-moments-of-better-call-sauls-final-season/ The 10 most shocking moments in the final season of Call Saul