Major companies including Spotify , Oracle and Comcast have appointed co-CEO s this year, drawing fresh attention to a long-scrutinized corporate strategy that aims to pair dual leaders with complementary expertise to take on the top job. But Emma Walmsley, chief executive officer of GSK , isn’t sold on the leadership model, which is based, in part, on the idea that the CEO role has grown too vast— even unsustainable —for one person to handle.

“I think there are few things more obnoxious in life than CEOs complaining about how hard their life is,” Emma Walmsley told Fortune senior editor Claire Zillman during Fortune ’s Most Powerful Women Summit on Tuesday.

Walmsley has served as CEO at GSK, a British drugmaker, since April 2017 and will step down in at the end of the y

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