Regarding Better Call Saul tho ---> gotta figger it is the brother that will be the tipping point.
Jimmy is walking this line between weasely scammer and noble, good intentions. He did take that money from the Kettlemens - but it could be easily justified in his mind as a victimless crime with the money actually going towards something moderately good or at least neutral.
We know where he ends up.
So something has gotta happen where his brother needs something that costs a lot of money - at the same time Jimmy is presented with an opportunity to get a big payday to do something life-changingly, unjustifiably unethical.
Maybe it also coincides with a fight with chicky-poo.
Bada boom, bada bing ---> we're on our way.
It's a theory.