User blog comment:Miskos3/Fairy Tail Chapter 379: Tartarus Arc, Part 3: Underworld King, Review/@comment-83.255.207.11-20140404083102/@comment-7418318-20140404155250

As far as pure power-level goes I'm very sure she's been on S-Class level for a while now. On Tenrou she was probably equal if not ahead of Levy (who was an S-Class candidate) in terms of raw power-reserves and since then she got Second Origin and more training.

But power-reserves alone - or even battle-prowess as a whole for that matter - aren't enough to qualify someone as S-Class Mage. As much as I'm a fan of her and endlessly try to argue down the Lucy-haters, it's still clear to me that she's not quite ready for the exam yet.

Putting that matter aside, I think this chapter will go a long way to quiet the "Lucy is useless" cryers... at least for some time.

While it might have been Natsu who delivered the finishing blow (and all the other blows too, save for a single one by Taurus), without Lucy he'd never have been able to overcome Franmalth.