Irish judge Louis told X Factor's official website that out of all the female judges, former Pussycat Doll Nicole is the one who has impressed him the most.
Louis said: "Nicole is the best female judge we have ever had on The X Factor – by a million miles!"
Wow, that's a big statement!
'Boomerang' singer Nicole joined the ITV show in series nine as a replacement for Kelly Rowland. She previously judged on the US version of the show.
Louis added: "She has an amazing worth ethic. She's like an athlete, the way she just goes for it every day. She will always work so hard – and I love that about her. She's going to fight."
Nicole won last year's show with singer-songwriter James Arthur. Her other act, Jahmene Douglas, finished in runner-up position. Not bad for her first year, right?!
This year she's mentoring the girls. Last weekend we saw her choose the final six who will travel to Antigua with her for judges' houses. This weekend we'll see her choosing the three girls who will go to the live shows.
Nicole and Louis now judge alongside Sharon (who returned for the tenth series after departing a few years ago) and Gary Barlow.
Louis - who is mentoring the boys this year - didn't reveal who he thinks the best ever male judge is. Presumably he'd choose himself though?!
This will be our last year of seeing Louis on X Factor as he confirmed earlier this year he'll be bowing out at the end of the current tenth season to focus on other work commitments. (Read: Louis Walsh confirms he's leaving X Factor).
Check out some sneak peek pictures from judges' houses below: