S06E22 Grave

"It was me who took you out of the earth. Now the earth wants you back." Darth Willow has everyone on the ropes, Buffy's stuck in a hole, Xander's KO'd, Anya is about to die trying to save the nerd duo, when she's saved by a handsome former watcher from the UK. Giles is back and he's all juiced up with magic and ready to fight Dark Willow. Only to be immediately taken down and all his borrowed magic absorbed into the now Super Saiyan Dark Willow (her power level is over 9 thousand!), she's powered up like never before and ready to destroy the world. But first she sends some swamp-thing elemental dirt monsters after Buffy and Dawn, you know so they can fight and talk. Meanwhile at burning man Spike is tripping out, hallucinating that he's fighting the fire dancers and then that he's cover in bugs. Giles, now dying, tells Anya that Willow has absorbed the essence of true magic, whatever that means, and that's the opportunity for a good boy to reach her. Willow is channels the magic into the remains of a satanic church, which we all know is how you destroy the world, when her bff Xander shows up. Using his heart and a story about kindergarten Xander emotionally breaks Willow so hard she loses all her powers and falls to the ground an emotional mess. Hooray, the world is saved! Oh, yeah and Spike, who is totally unaware of all this, gets his soul back