I personally am of the opinion that, though we are fairly powerful as guardians, we just keep getting lucky that we can outsmart our enemies. Throughout all of the raids we've done, there were mechanics that allowed us to defeat the most powerful of enemies. These mechanics are meant to destroy us in the lore, but we improvise and turn each enemy's weapons against them. Atheon tried to scatter us through time, but we got lucky and the relic that was created by Kybr was there to save us, and allow us to return and attack Atheon. Crota would have easily killed us if it wasn't for the fact that his minions had swords that could hurt him. Oryx sent light-eater ogres after us, but didn't anticipate us using the blights that they left behind to damage him. Skolas was our bitch and we could have killed him easily at any time. He was only moderately difficult because Variks likes to be a prick and make things difficult. I think that there won't be one particularly powerful enemy in this raid, but an enemy that is just as smart as we are and has the foresight to see that we can take advantage of anything and everything we possibly can to defeat even gods. Such an enemy would have contigencies upon contingecies that would work to thwart our every attempt to defeat them. It would be a battle of intelect as much as actual power.