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8 year oldThe Republican also complained about his microphone crackling and being at a lower level than his opponent's.
After an often bitter exchange, Mr Trump said he "might hit her harder" in the next televised debate.
Overnight polls with small samples were split on who won, but more rigorous surveys are due in the coming days.
Although Mr Trump told reporters immediately after the debate that Lester Holt had done a good job, he accused him of a left-leaning performance the next morning.
"He didn't ask her about the emails, he didn't ask her about the scandals, he didn't ask her about the Benghazi deal. He didn't ask her about a lot of things he should have asked her about. Why? I don't know," he told the US news programme Fox and Friends.
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He said Mr Holt had been much tougher on him: "You watch the last four questions, he hit me on birther [Mr Trump's past allegation that President Obama was not born in the US], he hit me on a housing deal from many years ago, that I settled on with no recourse and no guilt... that's a beauty to be asked, a 40-year-old lawsuit."
He also said his microphone was "terrible" and crackled, and that his volume was lower than Hillary Clinton's microphone. He blamed this for what some listeners thought were sniffles by Mr Trump during the debate.
Asked to rate Hillary Clinton's performance, he said he would give the Democrat a C-plus, but declined to grade himself. "I think I really did well when they asked normal questions," he said, but added he naturally struggled when asked "unanswerable" ones.
On what he might do differently, he said: "I really eased up because I didn't want to hurt anybody's feelings. So I may hit her harder in certain ways."
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Much of the debate centred on personal issues and attacks, with both candidates saying the other did not have the right character or temperament to become president of the United States.
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A CNN/ORC poll taken after the debate found that 62% of voters who had watched the head-to-head thought that Mrs Clinton came out on top, with just 27% giving it to Mr Trump.
This is based on interviews with 521 registered voters chosen as part of a random national sample. But only 26% identified themselves as Republicans while 41% identified themselves as Democrats.
An informal CNBC poll on its website found that 61% of people thought that Mr Trump won while 39% went for Mrs Clinton, but as CNBC itself points out, the poll is not scientific - anyone, including people outside the US, appears to be able to vote.
A post-debate survey by Public Policy Polling of 1,002 debate-watchers found that 51% of national voters thought Mrs Clinton had won, with 40% choosing Mr Trump and 9% undecided.
New York Times - The editorial board was unimpressed with the debate, saying "when just one candidate is serious and the other is a vacuous bully, the term loses all meaning". Opinion writer Nick Kristof said Trump had "hurt himself", others said Mrs Clinton had "crushed" her opponent.
Fox News - Pundits said Mr Trump had "struggled", "never took control" and "failed to exploit" the issue around Mrs Clinton's emails. "It helps to be prepared," one writer told the Republican candidate.
Breitbart - Writers at the hard-right news website said Mr Trump had "bludgeoned" Mrs Clinton on trade and accused Lester Holt of "shilling" for Mrs Clinton. Some 75% of readers said Mr Trump had won.
New York Daily News - The tabloid's verdict: "A grumpy loser! Trump pesters, interrupts Hillary throughout debate - but Clinton gets the last laugh."
The much-vaunted role of fact-checkers in this debate was perhaps not as central as many expected it to be.
Mrs Clinton's denial that she had called the proposed Trans-Pacific Partnership the "gold standard" of trade agreements was called out by fact-checkers, as was Mr Trump's denial that he had called climate change a hoax invented by the Chinese.
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