"That was mediocre at best," Simon said of the rendition, which ended out of tune. "Sorry, I prayed that the tempo wasn't gonna come in, it did. It was a horrible version of that song. In my opinion, genuinely, that was your worst performance by a mile."
Lil Rounds also met with some tough words from Simon, despite her skin-tight catsuit and faithful rendition of Chaka Khan's "I'm Every Woman."
"Sweetheart, I'm glad you had fun, because I think it's the last week we're going to see you," Simon said. "It had no originality. It was very copycat and I absolutely believe this is your final shot."
And Matt Giraud, who the judges saved from elimination last week, was also slammed by Simon for his R&B version of the BeeGees classic, "Staying Alive."
"I didn't actually like that performance," Simon said. "In the real world, that came over as a bit desperate. I don't think the vocals were great. I didn't hear any originality, so I'm not a huge fan of that I'm afraid."
The rest of the cast, however, impressed the judges, with Adam Lambert, who took on a soft and tender version of "If I Can't Have You," once again proving himself the most impressive to the panel.
"What I loved about this performance was it was original… most importantly, you're gonna remember it and the vocals were immaculate," Simon stated.
Kris Allen, who in recent weeks has become another "Idol" to watch, also took home praise for his unique, acoustic take on Donna Summer's "She Works Hard For The Money."
"It was original, it was well thought out," Simon said. "It was a fantastic performance."
On Wednesday, two contestants will be eliminated from the FOX reality competition show.
Related Content from AccessHollywood.com:
PLAY IT NOW: 'Idol' Judge Kara DioGuardi's Advice For Scott MacIntyre
PLAY IT NOW: 'Idol' Judge Kara DioGuardi's Singing Advice For Megan Joy