What if all the Special Characters in GW got into a huge fight, who do you think would win. Every single Special Character, from Abbadon to Calgar, from Ghathrakka to Creed, who do you think would be the last man standing? (Assume that Tyranids got to use thier 3 old Special Characters: The Red Terror, Old One Eye & The Death Leaper)
Thier two ways to figured out your answer... 1) based on "fluff"/backstory of the character, 2) based on thier in-game rules.
Some friends and I have thought it out, rolled it out and math-hammered it a few times and we have gotten different charcters but a few always make it into the final bunch. Mephiston of the Blood Angels, Helbrick of the Black Templars, the head of the Dark Eldar (who I forget his name at the moment) and Old One Eye always seem to survive till the very end in game terms. In "fluff" terms its gonna be hard arguing with anyonme beating the Nightbringer or Abbadon.