Stephen Bannon. Kirk Irwin/Getty Images for SiriusXM Former Breitbart editor Ben Shapiro unloaded on the right-wing website's chairman, Stephen K. Bannon, on Wednesday after news broke that Donald Trump had appointed him as campaign CEO.

"Bannon is a legitimately sinister figure," Shapiro, who left Breitbart earlier this year in a fiery exit, wrote on his website, The Daily Wire.

The conservative pundit added: "He is a vindictive, nasty figure, infamous for verbally abusing supposed friends and threatening enemies. Bannon is a smarter version of Trump: He's an aggressive self-promoter who name-drops to heighten his profile and woo bigger names, and then uses those bigger names as stepping stools to his next destination."

Trump "may be [Bannon's] final destination" or "it may not," Shapiro wrote.

"He will attempt to ruin anyone who impedes his unending ambition, and he will use anyone bigger than he is — for example, Donald Trump — to get where he wants to go. Bannon knows that in the game of thrones, you win or die. And he certainly doesn't intend to die. He'll kill everyone else before he goes," Shapiro wrote.

As chairman of Breitbart, Bannon has overseen the website's political coverage, which has leaned pro-Trump. At times, Breitbart has peddled conspiracy theories against Trump's political opponents.

Shapiro was a friend of Andrew Breitbart, who died in 2012. Shapiro left Breitbart earlier this year over disagreement about how the outlet addressed an incident with one of its former reporters, Michelle Fields, who was grabbed and pulled by Trump's ex-campaign manager, Corey Lewandowski, at an event. The website failed to stand by her, and Shapiro condemned it for not doing so.

Trump announced Bannon would join the campaign in press release on Wednesday morning. The New York businessman called him "extremely capable" and "highly qualified."