Some characters work better in pairs
Since I run most of the tabletop RPG's we play I don't get a chance to play on the same side as Lady Blacksteel very often. Once we started playing some MMO's we finally got to bypass this problem on at least one level and it's a lot of fun. Some characters we mainly play solo, some are part of teams with friends, and we've made a few characters planning to play them as duos. The first and probably best of these pairs was Nightfalcon and Stormbird.
For Nightfalcon my concept was a sort of combination of Tony Stark and Bruce Wayne - a genius inventor who witnessed his parents' murder at the hands of criminals. I see him as older when it happens, probably finished with high school but still living in the mansion and somewhat sheltered from real life. He's merrily pursuing his theories and gadgets when the real world intrudes in the worst way possible and he's suddenly left alone in his huge old house and has to start handling things like he never had to before. His research takes a darker turn as he discovers that certain alloys of metal can be made to radiate energy at certain wavelengths which can directly influence the human brain, mainly its emotional state. This energy can be projected at a distance, concentrated, dispersed in a field across an area - it can be manipulated with the length of the alloy antennae and the amount of energy put into them to create different effects. He calls this "dark energy" as one of the secondary effects is that it creates a shadowy hazing effect when certain amounts of power are used. He builds these alloy wire antennas into a protective and identity-concealing suit and begins to haunt the streets at night, taking revenge on the criminal element as Nightfalcon. Secretly he is still Wayne Anthony, wealthy genius.
One thing to note here is that he is not insane or obsessed at this point. He's just very very angry about what happened and seeks to ensure that it doesn't happen again, and he has the means to do so. He does struggle with whether to kill certain criminals or not but to date he has stayed on the side of "not". That could change at any time though.
About a year into his nocturnal crimefighting he meets a nice attractive girl with some ... problems. She appears to have some kind of power over electricity but she cannot control it and things tend to run wild around her, shorting out cellphones and computers and generally making mayhem at random times and to varying degrees of power. This also cause wild surges in her emotional state which makes her social situation even worse than it already would be with the aforementioned electrical problems. Being victimized by her out of control abilities once himself while in the middle of a fight, Wayne realizes something has to be done and upon examining her he realizes that a variation of his own alloys could allow her to control these powers. He implants a small control device near her brain to calm the outbursts, then he builds her a suit similar to his own with a variety of alloy antennae set to her own wavelength that give her an amazing degree of control over electricity. It's so fine that she learns to control air currents through static electricity, giving her a suite of powers akin to the storm gods of old. The first time she asks to go on patrol, The Nightfalcon of course says yes and a new super duo is born, many times more effective than either of them alone.
After a short time of adventuring together they are married and Lyssa moves in to take up residence in the mansion.
Years later, He's now in his 30's and on the streets is a hard-bitten, gruff, and somewhat grim character as he realizes he can probably never win his war - all he can do is fight until he falls. He has come perilously close to killing some of his prey, but Lyssa is his connection to reality and his past and everything he wants to be. He still isn't crazy, thanks to her, but he struggles with it sometimes and if anything were to happen to her it is likely he would drop his real life and fully submerge in his war on crime, and it would turn into a very deadly war in short order, going out in a blaze of fury and blood. Thankfully, his better half keeps him anchored in a better reality. There is also the ever-recurring discussion about children, which could help anchor him more, convince him to retire, or could send him over the edge even faster and even he isn't sure which is more likely. It's not a question that has been settled yet.
He knows they are in a dangerous profession but sees it as safer operating in a team. He trusts her to look out for herself but does not like to send her off alone in an unknown or dangerous situation. On the few occasions when she has been taken down or seriously injured he has nearly lost control and come closer to committing murder than at any other time.
She knows it dangerous but gets a kind of thrill from doing the dangerous work, being a mysterious figure, and working with her life mate at the thing he feels the most passionate about. She regularly underestimates her powers, which are probably stronger than his in most ways, but on the few times he has been taken down she has erupted like a raging hurricane, frightening herself and causing tremendous secondary damage to the area.
Other heroes see him as experienced, cool, and intelligent and generally trust his judgment, but a few have seen what happens when Stormbird goes down in a fight and they fear what might happen if it was serious or even permanent. Most policemen see him as an ally they don't have to worry about and will help the duo whenever they can. Stormbird is quiet around the media, unlike many other heroes. She lets Nightfalcon do most of the talking as she fears that she might say something that would give away their identity. He's short enough with the press that she sees less risk that way. That said, she secretly loves the role of savior and hero, and loves the game of "who is the mysterious duo" and reading the speculation online about who they really are.
They do work better as a team but in the long run there is the danger that one of them will fall, causing the other to erupt in a lethal and unrestrained show of force, probably ending the survivor as well, possibly harming innocents, and tarnishing their stellar legacy right at the end. Many wouldn't blame them for it if ti happened, but it's not the way they would want things to go if they were in their right minds. If a child were to come into the picture... well, it might be enough to hold back the explosion or it might mean another orphaned potential super-child grows up with a grudge and a legacy.