The hedge fund manager told CNBC's "Squawk Box" that he watched Trump's wife, Melania, introduce him as a generous, giving person in a campaign appearance over the weekend. Tepper disputed that, contending the Republican presidential candidate did not give money in the wake of some New York-area disasters.
"During Sandy, the big Sandy benefit, the big 9/11 benefit, not one dime. Not one dime! You can't tell me this is a charitable, generous person," the Appaloosa Management founder said, raising his voice to a scream.
"Trump masquerades as an angel of light, but he is the father of lies," Tepper asserted.
Trump has repeatedly boasted about his charitable giving on the campaign trail, even skipping a GOP primary debate to hold a fundraiser for veterans. But investigations, particularly from The Washington Post, have found Trump's real giving has not measured up to his talk.
In a subsequent interview on "Squawk Box," Trump campaign manager Kellyanne Conway said: "Mr. Trump has been very generous with his time and his money over a number of decades. … I've witnessed it first hand."
Tepper noted that Americans face a choice between "two people who have judgment issues" in Clinton and Trump. He said he does not like the Democratic economic platform and hopes the GOP keeps control of Congress.