Black Mask (Roman Sionis)

This year (2020) marks the 35th Anniversary of Black Mask (Roman Sionis),
whose origin was told in Batman #386 (cover-dated August 1985, with an on-sale date listed in the GDC as April 16th):




And, since this was the mid-1980s, you could no longer get away with a quick origin  story for a major bad guy.  The story in that issue continues with all Roman Sionis' misfortunes and screw-ups, plus how he was such a disappointment to his uncaring parents. (But don't worry. Mommy and Daddy Sionis don't get off easy, either!)

Black Mask didn't get an entry in the initial run of Who's Who: The Definitive Directory of the DC Universe (which also started in 1985), but there was this in Detective Comics #566 (September 1986) in the story "Know Your Foes":

A very underrated villain who I've always thought deserved more exposure. Every so often, someone remembers him and dusts him off, but he's never really been given the chance to fullfil his early potential. Doug Moench really was great at creating villains for the Dark Knight (whatever happened to the Night Slayer, anyway?)

from Who's Who in the DC Universe Update 1993 #1 (December 1992):

Oddly enough, Lucy and I watched the recent Birds of Prey movie, which features Mr. Sionis as its main villain, just last night. It wasn't as bad as we expected it to be!