Croc (Waylon Jones) a.k.a. "Killer Croc"

from Who's Who -- The Definitive Directory of the DC Universe Vol. V (July 1985):


The funny thing is, many of Croc's Who's Who entries list his first appearance as Batman #357 (cover-dated March 1983), but in the GCD they show an earlier appearance in Detective Comics #523 (February 1983):



Here's where he's seen in Batman #357 (March 1983):



And then we get Detective Comics #524 (March 1983):





Croc was the one responsible for the deaths of Jason Todd's parents pre-CoIE, and that led to Jason becoming the new Robin (replacing Dick Grayson in that role).
However, in post-CoIE continuity, when Jason lost his background as the son of dead circus trapeze artists and got a whole new backstory, Croc also lost that major part of his pre-CoIE backstory history.

One of the best Killer Croc stories in ages appears in the latest issues of Detective Comics. It's worth buying for the last panel alone.