I wouldn't make an ugly face if somebody handed me that vocal and said "make it sound better". There's
plenty to work with there. In fact, my primary mission would be to do as little as possible to it.
Pitch-correction wouldn't be my first stop. There are only a couple notes that could use a little help up, but for the most part Melodyne would probably do more damage than good unless used very conservatively. It's an aggressive style that neither wants nor needs to be perfectly on pitch. Making it so would only weaken the performance, IMO.
Given that overdubbing, double-tracking and re-tracking aren't options, I'd fall back to some basic techniques. A harmonic exciter / parallel distortion plugin could roughen it up a little. A subtle chorus or flanger could add texture, especially if preceded by some kind of harmonic distortion effect. I'd lay on some heavy delay on the "ooh yeah yeah"s, just because that's what Robert Plant would do.
If you're looking for specific product suggestions, here are a few things I'd want to have on hand for this type of vocal, if I wanted to take it into outer space:
ValhallaDSP UberMod
ValhallaDSP ValhallaRoom
FabFilter Timeless 2
D16 Redopter (or the newly-released Devastor 2)
Audio Damage RoughRider
But I wouldn't put any of them on from start to finish, but rather automate them to come in for emphasis.