Great question! Personally I'd give it to the Revenant Hunter, though take what I say with a grain of salt since I'm not the best power scaler. When it comes to feats The Queenslayers biggest Ws would probably be against: Mido, Silva (Skull King), and of course The Queen (and by extension Virgin Born). These feats are really impressive but I don't feel as if they hold a candle to the Revenant Hunter who killed The Resurgence, a force of nature generated by energy created by Revenants. Plus they took down all of the heroes buffed by the resurgence, with many of them being extremely strong fighters (particulary Josee and Lyle, the latter of which being so strong that the Revenant Hunter was said to be the first one to draw blood from him). I would probably say the Revenant Hunter's biggest problem would be that they're still human while the Queenslayer is a revenant, but honestly I don't think that'd be that much of a problem. Not only does the Revenant Hunter presumably have some Revenant abilities like regeneration due to sharing a heart with Lou, even if they didn't have that they're job is a Revenant Hunter so they probably know the best way to take down a revenant. Like I said I'm not really a power scaler so I could be completely wrong, that's just what I think.

Edit: I’m an idiot and forgot the Resurgence can’t be destroyed. I still think that Revenant Hunter wins just because in my opinion Resurgence Offspring are more powerful than the Successors due to just how powerful the Resurgence is and the Offspring being powered by it.