It’s rare, but here is a case in which plaintiff was granted summary judgment against the target attorney in a legal malpractice case.  in Anne Koplick Designs, Inc. v Lite ; 010 NY Slip Op 06356
Decided on August 10, 2010 ; Appellate Division, Second Department .  In its short, but stark decision the Second Department writes:

"Here, the plaintiffs made a prima facie showing of their entitlement to judgment as a matter of law on the issue of liability (see CPLR 3212[b]; Yiouti Rest. v Sotiriou, 151 AD2d 744, 745). In support of their motion, the plaintiffs submitted an expert affirmation of an attorney establishing that the defendant Justin N. Lite failed to exercise the ordinary reasonable skill and knowledge commonly possessed by a member of the legal profession by, among other things, advising the plaintiffs to default in a lawsuit commenced against them in California and advising them that a default judgment obtained in California would not be enforceable in New York, a clearly incorrect statement of the law (see Logalbo v Plishkin, Rubano & Baum, 163 AD2d 511; Yiouti Rest. v Sotiriou, 151 AD2d at 745). The plaintiffs’ submissions also established that, but for the defendants’ malpractice, they would have succeeded in defending the underlying claim. In opposition, the defendants failed to raise a triable issue of fact (see Alvarez v Prospect Hosp., 68 NY2d 320, 324)."