Ah, where to begin. I was never exactly an early poster here. Returning from my summer absence, I found 'myself' on the Scourge. A lackey. A hired goon. The shame. :(
The Scourge member was quickly declared a fake, yet the world was to be unaware that he wasn't the real thing.
The Grim Reaper came from an alternate dimension, and believing the world to be an corrupt, evil place, eventually came to the conclusion that the only way to change that was to take over. His long-running career of villainy there is mostly unrevealed and not really important right now. Except for his escaping defeat by jumping between dimensions, and ending up in the middle of that cosmic cube round-robin story that's in the archives. That's his only encounter with any heroes to date. Using the cube power, he re-made himself, gaining mastery over dark magic, evil science and hand-to-hand combat.
He then escaped, and was presumed defeated, and, finding himself in Null-Space, was chosen for a mission by the enigmatic Void Spectre. As brief as I can make it, the mission requires him to travel the dimensions, and protect each variant Earth from domination by the demon lords of the pit, by enslaving humanity, or, if too late, destroying the world. After judging countless worlds, he grows bitter and weary of this task.
On his arrival on a world, he raises a tower on the moon as a base of operations. Here, not long after his return, he was ambushed and replaced by The Unit, who impersonated him throughout Pierson's story. The one which blew up the moon.
Re-creating the moon through the power of dark magic, he defeats the Unit, sending him down to Earth, still in disguise, to get defeated and exposed as an imposter, then strikes back at Earth in vengeance, destroying several nations chosen at random. (Except France, which was destroyed because Pierson demanded it. Heh.)
Since then, he created the Moon Sentinel, a vast robot, designed to lead a metal army to Earth, and take the blame for the destruction of the nations. How well humanity withstood the machines' attack would form part of their judgement. Although thanks to a continuity lapse, they still haven't got landed yet. :(
Also, realising that Earth's heroes would investigate the situation, he created a team of his own, (though they know not of his involvement), for the purpose of killing heroes. Hunter/Killer, the villain of Green Ninja #3 was one of these.
That's it so far. Hopefully that'll do for now, although I can provide a summary of weapons, powers, minions, etc, if needed.
The Scourge-Reaper is a completely different character, and gets his own bio. Mentally coerced by the voices in his head to put on the costume and join the Scourge, he quickly became a minor, yet recurring member of Zemo's team, his power-scythe and martial arts skills rarely being used. No prizes for guessing where the voices came from.
After a long period of inactivity, he suddenly developed assertiveness and took over the remnants of the Scourge, for a mission that the voices tell him will finally make him important and powerful.
Everything he knows about supervillainy comes from cartoons and comics, and thanks to the voices, he is assured that he has seen the future, and will be the one to bring it about. His real name and history are as yet unrevealed, but I might just get to it in a Scourge-focused follow up to the end of Green Ninja.