Dr. Abraham Fletcher
Plastic surgeon. While earning cash through giving new faces to wanted criminals, he also used his metahuman powers to "remold" their personalities, creating a small, experienced crew of criminals to work for him. One of his operators was Vincent Ratioli, who tried to recruit Mark Simmons for further operations. Fletcher was eventually arrested in a raid on his office and is currently serving time.
Dr. Aaron LaPointe
Responsible for the clinical trial of Faroxil, a new drug to combat Shizophrenia. When one of his patients went unstable and killed a woman on the subway, LaPointe at first denied that the drug was ineffective, but eventually revealed that he was receiving payoffs from the CEO of the manufacturer to make Faroxil look good.
Pimp, and leader of a white slavery ring. He had the metahuman ability to walk though solid matter, but even that didn't save him when the SCU raided his headquarters - Mark Simmons was waiting outside with a sniper rifle and put a round through Fernando's head.
Colonel Manuel Rodriguez
An officer who lost a leg in an accident during the Invasion of Grenada, leaving him lame and reliant on a prosthetic. He went rogue and amassed a private army on Ragged Cay, where he began to search for an artifact called The Last Message of Nyarlathotep, which would allow its wielder to awaken Cthulhu - and make people understand the gravity of that threat. He was killed when Mark Simmons pinned his prosthetic leg to the bed of a truck - which was, at that moment, heading for a cliff at a rather high speed.
Michael "Bruiser" Hogan
Small-time crook and musclehead, apparently with an axe to grind with Mark Simmons. The two faced off on top of the under-construction Love Towers, where Hogan was revealed to be a celestial. Mark couldn't kill him with either normal or holy bullets, but Dante Vecci managed with one shot. Later, it was revealed that the alignment on Dante's bullets had flipped, making him shoot unholy ammo.
The most likely conclusion is that Hogan was an Avatar, but his agenda remains unknown, other than a sketchy connection to Ray Bradbury.
Lieutenant Mike Theissen
Navy SEAL and former romantic partner of Sharon. Although at first cooperative and even helpful in an investigation on a bizarre death aboard the USS Harry Truman, he eventually faced off against the team when it was revealed that he was the leader of a drug ring aboard. Avenger slammed him against a bulkhead, killing him.
His real name remains unknown, but Nephilim was a man who practiced an obscure form of death magic, apparently aiming to carry out a gypsy curse on the new Ambassador from Georgia. By the time of the hit, Nephilim had managed to collect a sizeable amount of mojo, but Lucifer interfered and allowed Nephilim to be captured. When Neph escaped from custody shortly thereafter, he was taken by the Angel of Death - Thanatos - and put into Limbo.
It is not known if Nephilim was merely a powerful Metahuman or an actual Dark Angel, i.e. an offspring of a human and a Grigori. Lucifer hinted that he was unaware of any actual Nephilim still surviving, so the former seems more likely.
Ray Bradbury ===
Don't ask, we don't know either.