Complex sentence: Nico di Angelo's fatal flaw is holding grudges, as Bianca tells him-which, in his case, can lead to not wanting help or not asking to be saved in deadly situations because he does not like someone.
Split into simpler sentences: Nico di Angelo's fatal flaw is holding grudges, as Bianca tells him. In his case, it can lead to not wanting help or not asking to be saved in deadly situations because he does not like someone.