The Mighty (Dark) Avengers

Part of the "Avengers Wave" that spawned out of the formation of the New Avengers, the "Might Avengers" is a group consisting mostly of anti-heroes and reformed villains.  Because of this roster some of nicknamed them the "Dark Avengers" in contrast to the much more notably heroic other Avengers teams.  As of now their roster consists of:

Iron Patriot(Hank Pym)-Ant Man.  Giant Man.  Yellow Jacket.  All are superhero identities used by Hank Pym over the years.  And all of them lack any amount of respect BECAUSE they were identities of Hank Pym.  Despite his bad reputation, Hank still wanted to continue being a superhero and help the world.  So in a move to start fresh he crafted for himself a new identity with some ideas he "borrowed" from Tony Stark.  Blending together the symbolism of Captain America and Iron Man he became the Iron Patriot.  In addition to making this new identity he also wanted to help fellow heroes with less than stellar reputations and thus the Mighty Avengers were born.  

Anti-Venom(Flash Thompson)-A long time fan of Spider-Man, Flash took his hero's example and signed up ROTC when he entered college.  After he graduated he was sent off to Iraq where he ultimate lost the use of his legs while saving his superior officer during an ambush.  This show of heroism made him the perfect candidate for an experiment a covert goverment lab was conducting.  In order to fight the growing symbiote threat, scientists there took a small sample of the Venom symbiote and bred it to become the prefect weapon to fight against Venom and the other symbiotes.  Once bonded to it, Flash regained the use of his legs along with powers similar to Venom's in addition with the power to heal people of wounds and sickness.  Unfortunately, part of the  original symbiote's aggression still remained in this new one and right after being bonded to it, Flash went on a rampage that resulted in the deaths of many of the lab's staff.  Feeling remorse over what he had done, Flash fled the lab and went off looking for some way to destroy the symbiote, even if it meant taking his own life.  Thankfully before that could happen, Iron Patriot found him and offered him a spot on his Mighty Avengers with the promise that they could help him control the symbiote and use it as the force of good it was meant to be.  After a lot of thinking, Flash accepted the offer and came up with Anti-Venom as his superhero name.  

Red She-Hulk(Betty Ross)-After freeing herself from her father's control during his "Hulkbusters" debacle, Betty Ross secluded herself from the world to better understand her new powers and abilities.  Though she freed herself from her father's mind control, she could still feel the berserker rage inside her, threatening to come out at any moment.  Now given an even greater insight to what Bruce had gone through all those years, she sought him out for help when she discovered he found a way to live peacefully with the Hulk.  In fact it was Hulk himself who taught her the technique she would need to keep her Red She-Hulk form while not loosing control.  When he offered her a spot on the freshly form "New Avengers" she declined as she wasn't sure if she was ready to work so closely with him just yet.  Before she left, however, she was presented with the gift a massive sword made from Stark Industries repuslor technology mixed with Uru metal from Asgard, which she lovely calls her "Big Ass Sword".  Though she turned down the invitation to join the New Avengers she easily accepted the offer to join Pym's Mighty Avengers as she saw it as a good opportunity to fit into the superhero community better but without the baggage of being around people who knew her before her transformation.  

Superior Spider-Man(Rick Parker)-One of the many clones created by the Jackal during the height of his "Maximum Clonage" scheme, this one lay forgotten in a secret lab for years until it was uncovered by a dying Doctor Octopus.  Wanting to transfer his vast intellect out of his cancer ridden body, Doc Ock first tried taking on Spider-Man himself but he was too weak to overcome the Wall Crawler.  After a similar encounter with the Scarlet Spider, he remembered the Jackal's fondness for cloning Spider-Man and set about finding one that hadn't been destroy yet.  He reasoned it would be easier to take over a dormant mind and body and almost succeeded when the clone suddenly sprang to life and out of the tube.  He made quick work of the deranged doctor then fled lab to get back to his home.  Of course he became distraught when he learned he was yet another Spider-Man clone and thought of just waiting to see if his body would degrade to to put him out of his misery.  But then another thought accord to him.  One that told him he didn't have to be "just a clone" and in fact could be just as much a Spider-Man as Peter could.  Better even!  He could be a Superior Spider-Man!  Taking the name "Rick Parker" to honor Peter's father, he rented a rundown apartment as his base of operations then set about crafting his own spider suit.  He ran into Iron Patriot not long after debuting as Superior Spider-Man and eagerly joined his Avengers team, reasoning that if he could help this third rate Avengers team be better than the "real" Avengers, then that would prove just how superior he actually was to the "real" Spider-Man.

Ms. Marvel(Karla Sofen)-After her experiences with the various Thunderbolts team, Karla came to release that part of her actually LIKED the admiration she got being a superhero.  And she had to admit to herself that she did take a certain amount of pride in actually helping people for a change.  Once the original Thunderbolt's ruse was revealed, however, she could no longer use her Meteorite name as people knew she was the villainous Moonstone.  Which of course meant she couldn't use her original Moonstone name either.  Thankfully serendipity struck when she found out that Carol Danvers had traded her "Ms. Marvel" name and costume for the new "Captain Marvel" moniker.  Taking the old mantle and costume of Ms. Marvel not only allowed Karla to continue her heroic exploits but also to screw with Carol's head which she saw as an added bonus.  When she was invited to join the Mighty Avengers she was skeptical at first but eventually joined when she realized it might help her public image overall.  Plus from a psychological standpoint she was curious to see just how this group of individuals would get along.  And just how she could manipulate them to suit her own goals should the need arise.