“The second Robin killed by the Joker came back — and returned as the anti-hero who decided Batman's rules were wrong.”
The sharpest difference from Batman — he uses guns and accepts lethal force when he deems it necessary. He draws his own moral lines.
Trained directly by Batman — already elite. After resurrection via the Lazarus Pit, his physical abilities were further enhanced.
He took the Joker's old alias and weaponized it — the helmet hides his face and was designed to instill fear in criminals who knew the name.
The Robin who came back from the dead — while the mentor who failed to save him still keeps his killer alive. His anger is valid but misdirected. He swore he wouldn't be Batman, yet what he really wants is Batman's approval. That contradiction makes him the most human member of the Bat-Family.