Played by Victor Rendina, Don Tattaglia is one of the Corleone family's main rivals. His family launches war against the Corleones after they refuse to lend their political clout to the Tattaglias' drug biz: They execute Luca Brasi and try to kill Don Corleone, severely wounding him.
In retaliation, Sonny Corleone orders the death of Don Tattaglia's son, Bruno. This leads, eventually, to Sonny's murder at the hands of Tattaglia's men. At this point, Don Corleone negotiates a truce… but the fight isn't really over. When Michael takes over, he orders Tattaglia's death along with that of his other enemies: a hit man shoots him and the woman who's in bed with him.