Apocalypse here is dieing and accepts death rather than the Celestials. However, the Celestials revives Apocalypse, and tells him that time has come for him to pay his part of the bargain (Which has yet to be revealed).
Have the original Beyonder vs. Celestials scans been posted yet? Even though the Celestials lost (or appeared to), they had some good feats, like reading Beyonder's mind to tell he wasn't really going to destroy the universe the first time, and attacking billions of times per second on multiple planes of existence.
The Celestials vs Pre-retcon Beyonder (by request.)
The Celestials don't win this fight...they dont exactly lose either, its more of a test by The Beyonder. However it does show The Celestials fighting an opponent higher than themselves and what they're capable of. Fighting on planes higher than the physical, the "billions of feints, parries and thrusts per second." Also, its should be noted they survived Beyonder's attack as well.
I don't think it's really the celestials that are doing the feints, parries, and thrusts. Reason being is that the beyonder is talking and explaining the battle. This suggests that he is the one doing the billions of moves in multiple plains of existence. This is further backed up by his quote in the aftermath of stating that no one could observe how impressive it was since it was on multiple plains on existence. I would imagine the beyonder is saying that he himself is impressive, not the celestials.
Also to note is that if you are attacking someone, you don't attack them with parries, feints, and thrusts. Those are DEFENSIVE maneouvers, not offensive. Why would a numerically superior force (the attacking celestials) attempt billions of parries, when parries are blocks of incoming assault? Those billions of moves are the beyonder's feat, not the celestials.
parries, feints and thrusts aren't entirely defensive, more deflective opposed to general 'blocking' or shielding. I would assume though both Celestials and Beyonder are maneuvering. Like Endless Mike said, whether The Beyonder is doing the defensive or offensive movements or not, someone would have to be attacking or deflecting the attacks moving at billions of times per second. The battle was taking place on levels of existence higher than the physical - meaning both are competing on that level.