Board Thread:Warhammer 40k General Discussion/@comment-27642965-20160211003725/@comment-4851119-20160309182435

Geoffreycoconut wrote: hmm, later last night (whence away from internet access) the time lords/gallifreyens occured as a possible Culture trumping option, not to mention an easy IoM beater, but I'm struggling for anything else, at least with the protagonist proviso, would be good to hear what else you've got. Oh, the Time Lords could most definitely do it. I'd bet on the Xeelee as well, they're only slightly below the Time Lords/Time war Daleks, but they're not really protagonists as such.

From what little I know of the Tenchi franchise the Jurai empire could take down most if not all of 40K with only slightly more effort than the Culture (they're actually more powerful in brute force terms, but seem to be slower).

If we're looking for factions below Culture level than Greg Bear's interpretation of the Forerunners and Precursors from Halo could take on anyone in the current 40K galaxy but would probably be outmatched during the War in Heaven.