Yui

SAO was bad anyway. She just made it even worse. The only good qualities the franchise ever had were the music, the animation, and the first episode. Anything else that had potential was swiftly discarded in favor of trivial mediocrities. 

basicly slaughtered sao, and made sao from decent to unwatchable

People only like her because they think she's cute, and that's a terrible reason to like a character. She was generic, and her arc made absolutely no sense. She is undoubtedly the worst character in the franchise.

I loved her! She was so adorable, and the fact that she willingly let Asuna and Kirito adopt her? Ugh! My heart! I love her, she was adorable and the perfect addition to an amazing anime

I actually cried when she died (I have no shame). I think she was the best charecter of the entire anime!