Archaon
The Everchosen, Lord of the End Times, Chaos Incarnate, Herald of the Apocalypse, Warlord of the forces of Chaos United, Scourge of the Empire.
He is Archaon... and he is not a fun guy to be around.
He started out as a devout servant of Sigmar, just as Failbaddon started out a good guy. That's about where the similarities end. One day Archaon, after a long day of being a bad-ass, decided to do a little light reading. Finding a little book whose cover caught his interest, he flipped through the pages. This book being, of course, completely evil. When Archaon saw the horrible blasphemies contained in the book, he flew into a RAGE! This rage was so intense, that even in another universe, the Angry Marines felt a disturbance unlike any they had ever felt before. Their rage was NOTHING compared to Archaon. He then proceeded to slaughter his family, renounce his name, and take off into the Chaos Wastes. He was then chosen to be the Everchosen of Chaos.
Accomplishments
He, by sole fact of being a badass, did what no other Everchosen could do. He gathered all of the Treasures of Chaos,in the process defeating hundreds of monsters in pitch dark, stole the horse Dorghar (steed of the apocalypse) from Agrammon, resisting the visage of Slaanesh, killed a Bloodthirster with its own whip, resisted every disease that Nurgle could throw at him, made it through a maze designed by Tzeentch, and then led the most ferocious and largest army of Chaos Warriors against the Empire. He fought and beat his counterpart Valten (who in an in-verse of him is cheap knock-off of one of the primarchs), who managed to kill Dorghar and smash Archaon's armor before losing (the Chaos warriors need to get around to stealing Ghal Maraz). And then the Mary Sue orc warlord Grimgor headbutted him in the junk. Since then, he has seemingly disappeared, and is supposedly gathering his forces for another attack.
So far, he also has the distinction of being the first non-Northman Everchosen. As his predecessors, Morkar the Uniter and Asavar Kul, are a Norseman and a Kurgan, respectively. So far, the only race that hasn't produced an Everchosen are the Hung. But GW seems to have forgotten that the Hung exist (or are secretly racist against Asian people Kurgans are Turks you fucking newfag).
Things for Archaon to do
-Find that orc who blindsided him and make him pay
-Find a way to bring orcs back to life, so he may torture, then kill, that damn orc again
-Repeat until bored (might take a while)
-By the time he's done, time will have flown by, say, about 40,000 years
-Find Abaddon, beat him to death with his own arms, and assume command so that Chaos might actually get something done
-Convert his chaos armor into chaos power armor Why would I swap my Chaos Plate for inferior protection?
-Start spreading Chaos the only way he knows how, at the tip of his sword, no more pussyfooting around chaos
-March on Holy Terra itself
-Beat the Tyranids into submission, then use them against the Imperium
-Out cheese the Gay Knights
-Beat the shit out of Gay Knights, so Chaos may have its long waited revenge
-Give Daemonettes their missing boobs (and actually make them attractive again)
-Kill the Tau. To. The. Last. One.
-Kill the Eldar
-Kill the Dark Eldar, he doesn't care that they are evil, he's more evil
-Kill the Necrons
-Kill the Orks (in memorium of his old friend Grimgor)
-Pimp slap Valkia the Bloody, so that she may finally learn a hoe's place.
-Have a drink with Wulfrik.
On the tabletop
In an interesting irony, though probably not intentional, Archeon is also in a lot ways the opposite of Abaddon, not in a bad way. Where as Abaddon tends to get changed fairly heavily each edition, Archeon stays the same with each book, with the only changes to him being armor save's not including bonus for him being mounted or whether or not you can field him on foot. Also, where as Abaddon is characterized by his hitting power, while being respectably tough to kill, Archeon hits hard (base attack ignores armor and can double attacks for the rest of the game, though if does any 1s on to hit rolls have to be directed at him or his unit), but his most impressive trait is how freaking hard is to kill. While his statline is only slightly better than a normal Chaos lord, he has a 1+ armor save, a 3+ ward save, all to hit rolls against him have a minus 1 and he can't be wounded on better than 3+. Sadly, while an indestructible death machine, his cost keeps him from getting much use.