Character Profile: Dio Brando

In short, Dio is a massive dick. He lacks any sense of empathy, is sadistic, violent and cruel. He turned thousands of people into zombies just for his amusement. He constantly abuses the protagonist (Jonathan), then plots to kill him and his father. He's later reduced to only a head and opted to behead Jonathan and steal his body. He succeeds, but is trapped at the bottom of the ocean in a coffin for about 100 years.

Later in the series, he returns after being pulled out from the ocean with the terrifying new power to stop time. He forms a cult of deathly loyal followers as well as a ring of mercenaries to prevent the main cast from reaching him. After they fail, he fights the main cast (or rather, what remains of it) himself. He manages to reduce the cast to a single character (although one is incapacitated and another is revived using his blood) he is unexpectedly defeated after being hit in his wounded leg, causing him to split in half.

Even later in the series, he has impact on the entire story long after his death in 1987. He causes the Joestar bloodline great suffering even when he's long dead, and indirectly causes the entire universe to almost be reset.