MSNBC’s Lawrence O’Donnell has taken Donald Trump to task for what he described as the president’s “worst” lie about the 9/11 terror attacks.

On Tuesday’s broadcast of “The Last Word,” O’Donnell branded Trump’s claim during a 2016 GOP primary campaign debate that he lost “hundreds of friends” in the collapse of the Twin Towers as “evil.”

“As soon as Donald Trump said that in the campaign debate in South Carolina, I said he was lying,” said O’Donnell. “I didn’t know how many friends he’d lost on 9/11, but I knew it wasn’t hundreds.”

Trump changed his story the following day to claim he’d lost “many, many friends,” but O’Donnell still doubted it.

“I still didn’t know how many friends Donald Trump might have lost on 9/11,” O’Donnell continued Tuesday. “But knowing the way Donald Trump lies as I do, I suspected then that the real number was zero, and then I checked, and the real number was zero. Donald Trump did not attend a single 9/11 funeral, not one.”

When he “held that lie up to Donald Trump’s face, even he could see how evil that lie was,” O’Donnell added. “And even Donald Trump knew he could never try to tell that lie again. And so he never did.”

Trump’s history of controversial comments about the attacks includes his baseless claim that “thousands” of Muslims celebrated the atrocity in New Jersey, and falsely bragging about his building becoming the tallest in downtown Manhattan in the aftermath.

Check out the clip above.