X Factor's 10th anniversary show turned sour as judges put the boot in to Tamera Foster for forgetting her lyrics for a third time.
The special commemorative show saw contestants reliving history by meeting previous contestants and covering their songs.
It featured a performance by Olly Murs, who lost to Joe McElderry in December 2009, after missing his brother's wedding to make the semi-finals but went on to sell 10 million records worldwide.
But the judges' generally glowing feedback last night stopped for Foster, who sang James Arthur's Impossible. The 16-year-old from Kent had fluffed her lines once in her arena audition and again in last Saturday's show.
Louis Walsh said: "You are the person with the most potential in this competition to be a worldwide superstar. But what happened to the words?
"It's so frustrating to watch someone who can be a potential superstar messing up her words. You can't do it any more!"
Take That frontman Gary Barlow was most critical, saying: "It's hard to watch, it's really hard to watch. I don't know how to solve this problem. On the live shows it's excruciating watching a car crash happen."
Sharon Osbourne urged her: "Don't get down on yourself. You tick all the right boxes, you've got it all going on. But just think - if you were lip syncing, there'd be something else coming out."
Walsh also tried to stir up trouble after Sam Bailey's performance of Leona Lewis' Bleeding Love by telling Foster she should watch it and learn.
But he was gracefully rebuffed by Bailey herself, who wished she had Foster's voice when she was 16 and called her younger competitor "amazing".
And Nicole Scherzinger offered much-needed support, saying: "I'm proud of you tonight, because you kept going, and you fought through it, and you ploughed through it, and you know what? You're only 16, little pumpkin pie.
"There's a little demon we've got in there with them lyrics, but we going to conquer that together. You get through this and nothing will be impossible."
Foster said: "I think I just got inside my head a little bit. I am shaking - I put everything into that song."
Other contestants had face-to-face advice with their forbears, but Foster's model James Arthur had pulled out due to "acute exhaustion" following a homophobia row.
Arthur cancelled all engagements yesterday after a week of Twitter fury over a diss track calling Croydon battle MC Micky Worthless a "f***ing queer" and "Taliban".
Worthless told NME magazine: "I was like, 'come on man, why are you bringing my actual race into it?' You can tell he's not very smart because I just don't know how he thought that could fly."
Tonight's show will feature performances by former contestants JLS and One Direction.
Other singers got warmer treatment. Host Dermot O'Leary called 17-year old Nicholas McDonald "the best contestant I've ever worked with on the show".
McDonald, who was invited to sing Flower of Scotland at his national stadium in Glasgow last week, celebrated his 17th birthday today.
That did not stop Louis Walsh referring to him as 16 after his performance of pre-twerking Miley Cyrus ballad The Climb.
Osbourne said: "Week after week, you are so reliable - you never let yourself down. Every week, Louis picks you the best songs, and you are just there, solid as a rock.
"You little wild man, you."
Seventeen-year-old south Londoner Hannah Barrett won high praise for a production of Hallejulah that was closer to the layered backing vocals and synthetic beats of Leonard Cohen's original production than the Jeff Buckley style of 2008 winner Alexandra Burke.
Her sponsor Scherzinger was most effusive, joking: "You know it's good and it touches you when there's snot, you know?"
"That song has been done a million times and no one can do what you just did. You didn't overdo it, you didn't over-sing it. You kept the integrity of the sung and the lyrics.
"You sung that song like a prayer, and tonight you just set me free and you let me go. Thank you."
Meanwhile Luke Friend revealed he recovered from last week's placement in the bottom two when he saw a tweet by Adele calling him "ridiculously good".
Friend sang a grungy version of One Direction's That's What Makes You Beautiful, leading Osbourne to call him "the dark horse in this place".
Barlow took Rough Copy to the Winter Wonderland fair in Hyde Park and forced them to go on all the rides before they met 2011 winners Little Mix.
Walsh told them there was "a massive gap in the market for a group like this in the UK", but Osbourne admitted she found the song choice "awfully whiny".
Bailey, the last remaining over-25, built on her "incredible" performance last week with a solid Lewis impression praised by all the judges.