The 1990s were a dark and gritty time for comic books. Anti-heroes like Venom, Lobo and Spawn lept to the forefront while old school characters like Superman and Captain America struggled to remain relevant. But this era was a unique environment in that some of those characters could only be popular during said era. It's not to say that they don't still get used from time to time in modern comics books. It's just that their heyday is a time long since past, similar to the Attitude Era of WWE. Unfortunately, those DC characters that typified the 1990s did not age particularly well.
10 Conduit
Kenneth Braverman was born in Smallville the same day an infant Superman's ship crash landed there. Kenneth and Clark went to school together for years. Once they reached their teens, their friendship turned competitive and Kenneth became jealous of Clark. He also started developing serious health issues. In college, he joined a government program that manipulated his illnesses and turned them into powers. This is how Conduit was created. Naturally, he made a beeline for Superman and tried to fight him, which didn't work out well. Conduit didn't last a year, let alone a decade, in the comics.
9 Lady Blaze
Part time bartender, part time demon that collects souls, Lady Blaze typified the 1990's era in DC comics. She was powerful, evil and violent, her plans pitting her against Superman and Shazam. She helped explore the mystical side of DC Comics in time where that didn't happen very often.
But the 15 minutes of fame Lady Blaze gained in the 1990s were over as quickly as they started. Outside of a few sporadic comic book appearances, Lady Blaze has remained a largely unused characters since the Y2K hit. Perhaps she's due for a resurgence one of these days.
8 Fate
This doesn't seem like a name that should be on this list. DC's venerable sorcerer has been around since 1940 and is still in use in one form or another today. But the version of him that popped up in the 1990s could only have existed in that decade. After the events of Zero Hour, a man named Jared Stevens took on the mantle of Fate by accident. He took the artifacts associated with Doctor Fate, like the classic helmet, and forged them into a golden blade and ankh-shaped throwing darts. It's the comic book version of adding the word "extreme" to a bag of potato chips. When Jared died, the artifacts returned to their true form and went back to Doctor Fate's sanctuary, like he never existed.
7 Cyborg Superman
After Superman gave his life to stop Doomsday, four new Supermen popped up. One of them was known as the Cyborg Superman since he was part organic Man of Steel and part robotic Man of Steel. At first, people thought this might be Kal-El resurrected but it eventually came to light that this was actually Hank Henshaw, an old enemy of Superman's.
He created this new body for himself in the depths of space, then came back to destroy Superman but found him already dead. As important as this character was during that era, he has struggled to find relevance ever since.
6 Bloodwynd
A member of the Justice League during Doomsday's arrival on Earth, Bloodwynd was one of the heroes to first face him and fail. Despite this, he is quite powerful thanks to the gem on his chest that gives him an assortment of abilities like flight, strength and durability. Additionally, Bloodwynd is also a talented necromancer who can call upon the dead when necessary for aid. All of this screams 1990s. A mysterious, mystical hero with an unknown level of power and an aggressively violent name. Outside of a short lived time with the Justice League, Bloodwynd has been largely forgotten over the last 20 years.
5 Doomsday
This character is simultaneously one of the greatest villains to come out of the 1990s and the villain that may typify it the most. A monstrous creature that crash landed on Earth, no one knew what he was, where he came from or what he wanted. All that was known about Doomsday was that he tore through Earth's most powerful defenders on his way to Metropolis.
Finally, Superman caught up with him and they died at each other's hands on the steps of the Daily Bugle. Doomsday was a silent, devastating force with no backstory, at first, that wreaked destruction with no plan or nuance, a character that had been largely irrelevant since the story that made him worldwide news.
4 Mr. Zsasz
While Doomsday was a force of pure, unthinking brutality, Mr. Zsasz was far more particular about his work. A sadistic serial killer, Zsasz believed that life is absolutely pointless and tried to help people escape this unfortunate condition by killing them. Every time he took a life, he carved a mark into his own flesh. There are a lot of marks in his flesh. The misdirected malevolence played a huge part in Batman's rogues gallery in the 1990s. Zsasz didn't have plans beyond slaughter. He was a killer who like to to kill essentially just for the sake of it.
3 Lobo
The Last Czarnian is about as '90s as it gets. While he still maintains a certain level of popularity today, the era that birthed him and put him at the forefront of DC has long since passed as has prominent use of the character. He originally popped up in the 1980s as a straight up villain but disappeared quickly due to a lack of interest in him.
Lobo returned in the 1990s as an anti-hero character, which made him an almost overnight sensation. The almost unkillable mercenary and bounty hunter remained on top for the better part of a decade, and still finds himself in use today but he doesn't move comics the way he used to.
2 Bane
The man who broke the Batman. Quite literally, in fact. Bane picked Batman up and snapped him over his knee, paralyzing him for a time. But despite his huge, hulking appearance, Bane was a cold and calculating man. He released waves of villains to wear Batman down, making sure he was not at his best when they faced off. His plan was a raging success and put Bane in control of Gotham. While no one would suggest that Bane has not been used with some prominence in the last decade or so, his time as the greatest of Batman's enemies was short and sweet.
1 Azrael
Born and bred by The Order of St. Dumas to be the next perfect assassin in a long line of perfect assassins, Jean Paul Valley took on the mantle of Azrael. When Batman fell to Bane, Bruce Wayne tapped Valley to replace him as the Caped Crusader. This ended poorly as Valley snapped, becoming an extremely vengeful protector of Gotham. When Bruce returned, he had to defeat Valley to get the mantle back, then recruited him as another member of his Gotham team. Numerous attempts to resurrect the character have been made over the past 20 years but he just can't seem to survive outside the 1990s.