This one?
That's the one!
Mile Cyrus just makes me cringe, massive pop tryhard and everything yeah, but what exactly is paticularly bad about this performance? Have to bare in mind that singers like that usually just lip-sync or avoid shows like this altogether, X Factor itself uses lip-sync for the none essential performances. Sounds like there's a little recorded backing in parts, and some deliberate echo to try match up to the song, but as much as I dislike her, she's actually able to sing a song that's suppose to be her's.
She should of avoided it altogether.
What was right about the performance? It sounded like her voice were put through a cheese grater. She were behind and had to speak fast to catch up. Admittedly that was only once that she did that, but still. Then she went to sing and coughed up a fur ball.