I was asked about this on a panel and said that my protagonists do their own psychotic dirty work. Parker was and is an important writer in the field, and he made it possible for other writers -- like me -- to write private eye novels when the form might otherwise have died out...he's like Spillane in that regard. But to me the Hawk character is inherently a racist conception -- the black guy who does the white guy's dirty work. And the character itself is lifted from blaxploitation movies. That this aspect of Parker's work had such an impact -- with writers as popular as Mosley and Crais imitating it -- is frankly bizarre to me.
I'm a Parker fan, and I liked Hawk when he debuted in Promised Land, but I agree with Collins that, in the course of the series, Hawk too often excuses Spenser from difficult moral choices. Without Hawk's number in his Rolodex, Spenser would have to do his own dirty work. Without Hawk, Spenser would be a stronger character, and so would Elvis Cole, Patrick Kenzie, Myron Bolitar, and so on, and so on.
At a panel last Saturday morning at Bouchercon, Robert J. Randisi said Parker's legacy was giving the P.I. novel an unexpected setting, not California or New York, but Boston, opening the door for future writers to evoke the nuances of any place they chose. I'd say the avenging sidekick is part of Parker's legacy in the negative sense.