Kelly Clarkson on 'American Idol': What helped the first 'Idol' winner succeed?

Clarkson returned to 'Idol' to serve as a guest judge and her performance won widespread praise. Not every 'Idol' champion has sold as many albums as Clarkson has – what led to her success?

The newest episode of “American Idol” featured the return of a familiar face.

Kelly Clarkson, who won the first season of “Idol” and has gone on to be one of the program’s highest-selling alumni, served as a guest judge on the Feb. 25 episode and also performed her song “Piece by Piece.” 

Her performance was positively received by the show’s judges (Jennifer Lopez, Keith Urban, and Harry Connick, Jr.), who gave her a standing ovation, as well as by critics. 

“Clarkson [brought] the house down,” Minneapolis Star Tribune reporter Randy Salas wrote, while Hollywood Reporter writer Kayla Kumari Upadhyaya wrote that Ms. Clarkson’s rendition was “powerful.” 

Mr. Urban also took to Twitter to compliment Clarkson. 

Fox’s music competition show, which is airing its final season this year after 14 seasons and industry-dominating ratings, has launched the careers of several major stars. While rivals such as NBC’s “The Voice” is doing well in the ratings, “Voice” has yet to name a winner that comes close to the selling power of Clarkson or fellow "Idol" champion Carrie Underwood. 

How did Clarkson, the first-ever winner of “Idol,” succeed in the industry?

One aspect that has appealed to fans may be Clarkson’s seeming authenticity. The singer previously battled with her record company, with Clarkson fighting for the right to include certain darker tracks on the 2007 album "My December."

“The drama, however, has been key to securing the loyalty of the global fanbase,” Guardian writer Alex Macpherson wrote. “Her fight not to be moulded is now a key part of her public persona.” 

And two aspects of her career – her voice and some of her collaborations – may have secured her success as well. 

New York Times writer Jon Pareles wrote of Clarkson’s 2015 album “Piece by Piece,” “The versatile voice that made Ms. Clarkson the first winner of ‘American Idol’ can sail through just about any arrangement,” while Jamieson Cox of Billboard wrote that Clarkson’s music has “always has been characterized by her vocal strength and versatility – few bells and whistles are needed to convey just how powerful her instrument can be.”

As for some of her collaborators, Jody Rosen of Rolling Stone praised the work of Max Martin, who co-wrote such songs as Clarkson’s “Since U Been Gone” as well as various hits including Britney Spears' "...Baby One More Time." "She has made brilliant singles, and may yet record a great album," Mr. Rosen wrote of Clarkson's 2009 album "All I Ever Wanted." "It's no mystery how to start. Three words: more Max Martin." 

Meanwhile, Rolling Stone writer Chuck Arnold wrote of her 2015 work “Piece,” “Another highlight, ‘Invincible’… is a triumphant power ballad co-written by go-to pop-diva tunesmith Sia.”