This is like a no contest.
Gaius Octavius, though his seed spawned the likes of Augustus, Caligula, Claudius and Nero, never really achieved the great heights of his progeny. He was basically a diplomat who died on his way to Rome, where he was to be voted in as consul. Maybe.
Otto Octavius, or Doctor Octopus, is one of the great comic book villains. Coming from a home with an abusive father, Otto turned his hatred of his father's behaviour into a passion for higher learning. Inspired by The Vitruvian Man, the great da Vinci sketch, Otto fashioned mechanical arms to help him with his atomic research. An explosion caused the arms and the harness to be fused onto his body.
I like Doc Ock's origin a lot because interwoven within the typical crap, is an interesting relationship with Mommy. She protects him as best she can from dad, but she also has some latent hatred for the sort of man her husband is. When Otto meets a woman, she's not good enough for Mommy. Otto eventually 'kills' his mother by getting angry at her for dating someone beneath her station - unforgivable and hypocritical behaviour to Otto - as she has a heart-attack during the exchange.
Alienated from parents and companionship, the accidental explosion rewires his brain, either due to latent mutant abilities or just the brian's coping mechanism in having to deal with extra limbs. He embraces his villainy with all arms, yet manages to retain his depth as a human being.
In the Sam Raimi movie, Otto is a brilliant portrayal of the classic villain. The sort who doesn't even know he's the villain, because his pursuit is noble. Though not always portrayed this way in comics, it solidified him for many as the wonderful character he is.
Short Answer: Otto Octavius.