Writer: Michael Fleisher
Artist: Dick Giordano
Publisher: DC Comics (1980-1982)
Includes: Brave and Bold #166-193
The Nemesis was a story that ran in the back of Brave and Bold at a time when DC was doing this with a few of their books. It was cool that not only did this back story run separately from the front story but it popped up into the main title on several occasions, including the Nemesis's finale, where he supposedly died.
History (clipped from Wikipedia):Thomas Andrew Tresser is a vigilante, turned operative for the U.S. government and a master of disguise. His default costume is a black turtleneck sweater with a balance as a chest symbol and a chest holster. He was an applicant to an unnamed government agency whose brother Craig was an undercover agent infiltrating a criminal syndicate called "the Council".
Craig was brainwashed into killing their family friend Ben Williams and was subsequently killed in self-defense by fellow agents.
Tom thus became "Nemesis", preferring to use an alias instead of his dishonored family name. With the assistance of Batman, he cleared his brother's name and saw the men responsible for his brother's death dead.