Complex sentence: Soon after his father's death, David becomes angered at Nate's sudden, permanent return as well as their father leaving half of the business to Nate, which David takes as a trivialization of the sacrifices he made for the family business.
Split into simpler sentences: Soon after his father's death, David becomes angered at Nate's sudden, permanent return. Worse, their father leaves half of the business to Nate, which David takes as a trivialization of the sacrifices he made for the family business.