He’s one of the best parts of Dressrosa. I know this site tends to obsess over powerscaling issues, but all that is secondary to what makes him great.
His speech at the end of Dressrosa is easily some of Oda’s best writing. His visual quirk is the best of the Admirals (blinding vs eye mask, marine hat, shaded glasses & sunglasses) because it’s the most meaningful.
His epithet is of the most ferocious creature but his demeanour and personality is the gentlest.
For me, he’s the best character introduced post-skip ( which I guess may not be much considering a lot of the rest are disappointments).