I actually thought of an alternate ending to Grave and ideas for season 7 in a blog post I made oh so long a go:
Xander does his speech, Willow breaks down in his arms, the magic leaves her system and the stress on her body takes its toll. Xander holds his best friend in his arms. De-magiced Willow smiles at Xander, a tear trickling down her cheek and simply says “Thank you”. Xander whispers “I love you” one last time before Willow closes her eyes. Xander weeps with his best friend in his arms.
Season 7 would have brought the group back together. First mourning the friend they lost and then learning to carry on without her. As a result, the final season would have been magic light after such a magic heavy season, focusing more on slayers fighting vampires. The First would ruffle everyone’s feathers by appearing as both Joyce and Willow, leading to a determined Scoobie gang fighting the ultimate evil, spurred on by the memories of the people they’ve lost. Slayer strength and slayer strength alone wins the final battle. The series ends with a montage of past characters, with Kristine Sutherland and Alyson Hannigan sharing a speech off screen over it that ends on the scene that the show actually ended on: Buffy’s face looking into the horizon and the last narration, a nod to Buffy’s previous speech: “Be brave, live…for me.” Buffy smiles. Credits.
Anyway, I wrote that ages a go, just a bit of self indulgent fan fic-ing really 😛 I don't know if I'd actually want to kill off Willow these days, but I wasn't fond of her season 7 self. But then she wouldn't be in Angel: Orpheus either, which would be sad. I dunno.
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But back to the question. I like Dark Willow, but I don't have much sympathy for her after Villains. In Villains she is sympathetic IMO, but by the time we get to Two to Go and Grave, she's the straight up big bad. I personally thought it was awesome, Buffy having to fight her best friend. As others have said, the bit I have a problem with is the lack of consequences in season 7.