"I no longer think he's funny,"the Democratic front-runner said Thursday night on the show.
Clinton took aim at Trump's recent call to ban all non-citizen Muslims from entering the U.S., a proposal experts say is unconstitutional and that critics say is also immoral and could pose a threat to national security.
"Now he has gone way over the line," said Clinton. "What he's saying now is not only shameful and wrong, it is dangerous," she said, citing the effect his comments may have on would-be jihadists.
"This latest demand that we not let Muslims into our country really plays into the hands of terrorists, and I don't say that lightly," said Clinton, calling his comments a potential "propaganda tool."
In the wake of Trump's comments earlier this week, some Republicans, including Jeb Bush and House Speaker Paul Ryan, have strongly condemned Trump's comments.
Yet others, like Republican National Committee Chairman Reince Priebus, have been more measured in their rebukes.
Democrats have quickly moved to try to associate the entire Republican field with Trump's stance, with the main super PAC supporting Clinton, Priorities USA, releasing a recent ad titled "Meet the Trumps."
Democrats have called on Republicans to say they'll refuse to support Trump if he becomes the nominee.
"Other Republicans really need to stand up and say: Enough," said Clinton.
She covered several other subjects during the interview, including guns, New Hampshire trivia and what qualities might make Bill Clinton a good First Husband; but, the State Department has told Senate investigators it cannot find backup copies of emails sent by Bryan Pagliano, the top Hillary Clinton IT staffer who maintained her email server but has asserted his Fifth Amendment right and refused to answer questions on the matter.
State officials told the Senate Judiciary Committee in a recent closed-door meeting that they could not locate what’s known as a “.pst file” for Pagliano’s work during Clinton’s tenure, which would have included copies of the tech expert’s emails, according to a letter Chairman Chuck Grassley sent to Secretary of State John Kerry that was obtained by POLITICO.