How did Dio and Jonathan first meet?

When Dio was twelve, his dying father Dario Brando sent him to the Joestar household with a letter claiming an old debt. George Joestar (Jonathan's father) took Dio in as an adoptive son out of gratitude to Dario — completely misreading the situation. From day one, Dio was strategizing to take everything the Joestars had.

What was Dio's strategy against Jonathan?

Systematic destruction. He burned Jonathan's dog Danny. He kissed Erina (Jonathan's love) to take away Jonathan's first kiss. He beat Jonathan publicly at boxing and rugby to establish dominance. He poisoned George Joestar. He used the Stone Mask to become a vampire. His campaign against Jonathan wasn't passion — it was calculation.

What is Jonathan's response to Dio throughout?

Genuine love that never becomes hatred. Jonathan consistently tries to understand Dio, help him, and reach the person underneath the cruelty. Even at the end, he holds Dio's severed head on the burning ship, refusing to let him die. His final act is compassion for the person who destroyed his life.

What does their dynamic represent thematically?

The irreducible conflict between two philosophies: Dio's — that everything is a transaction, that love is weakness, that dominance is the only honest relationship; and Jonathan's — that genuine care is real, that people can be reached, that the world is better than its worst examples. Jonathan dies. But Dio's worldview also dies, eventually, through all the Joestars who follow.

What makes their rivalry one of anime's greatest?

The asymmetry. Jonathan never becomes what Dio is. Dio never becomes what Jonathan hoped. There's no meeting point. The rivalry is between a man who believes in people and a man who doesn't, and both are completely sincere. That kind of clean philosophical opposition is rare.