Dormammu stalemated Eternity. Nekron would definitely hv a lot of problem with Dormy so add Trigon and it's becomes too much for Nekron to handle imo. Don't really know too much about Neron but he seems to be a non factor.
@atomix: oh my, ok i see where you're getting at :-P, how bout Surtur without Twilight Sword(he still could project cosmic energy if i'm not mistaken) or Nekron or maybe Dormammu and other high level sorcerers such as Classic Dr Strange :-/
@sirneko: can't argue with you there, i've seen WAY too many battles involving high level cosmic beings and it's almost impossible to rank anyone above another, but nevertheless in my opinion ya i do agree Beyonder wasn't truly omnipotent, it's just that by feats and arguments' sake he seems to be as close as a character can get to omnipotence without actually being omnipotent on the vine :-/
unless it's any being equal to or greater than Lucifer Morningstar and Michael Demiurgos in DC, i think i'll go for Pre Ret Beyonder here... Btw isn't he banned or something, for me Beyonder was one of those characters that blurred the line between nigh omnipotence and true omnipotence. Sort of like the Presence because now apparently there's the Primal Monitor.. It's all really confusing really.. :-/