Black Mask. Hush irritates me because he shows up for one story every few years that's heralded as this big game-changer but is usually nothing special. Started back in the very first "Hush" arc, which was a huge letdown given that I knew Loeb mainly from The Long Halloween before then. Pretty enormous difference in quality there.
Black Mask, by contrast, is just around all the time without making too many waves, so when he does have a game-changing story, it feels earned. He's a good crime boss for Batman's world.