In London, political commentators in the left-leaning Guardian newspaper said that Trump became "unhinged" mid-way through the debate. One writer, Jill Abramson, said Trump "could not help but show himself to be unfit for office."
"Driven, as usual, by ego, he unwisely made the debate about himself," she noted, although she also criticized Clinton for appearing "too pleased with herself" as she smiled while listening to Trump get tangled up at times in his responses.
There is a general concern among both Europe's left-leaning and center-right media – as well as the business world – that, if he got to the White House, Trump could be a loose cannon judging from past controversial comments he has made on women, migrants, Muslims and foreign countries.
Read More'Apocalypse now?' What Europe's media thought of the Trump speech
In light of by-now-notorious comments, Europe's media largely mocked Trump's assertion that he had a temperament better-suited for the presidency than Clinton.
"Trump was on the defensive throughout, shouting and interrupting his rival - all of which made his claim that his temperament was his strongest asset even more laughable," Chris Graham wrote in the right-leaning Telegraph newspaper.
Recent polls show that the two candidates are neck and neck in the polls ahead of the November election, making the televised debates a key opportunity for the candidates to persuade undecided voters.
Another writer in the Telegraph noted that Trump might still be able to win over undecided voters, despite his under-performance last night.
"Clinton showed her class on foreign policy and did very well to rebuff Mr Trump's repeated attacks. Her meticulous preparation showed.
Objectively she won the debate by a mile," Barney Henderson wrote. However, he added that "having watched Mr Trump win debate after
debate for more than a year when his performance simply seemed waffling and offensive, I think once again what he said tonight could resonate with some of the wavering, disaffected voters."
Italy's press, including La Repubblica and the Corriere della Sera newspaper led their coverage of the debate on issues which caused sparks to fly between Clinton and Trump: "Employment, the economy, racial tensions and terrorism."
As La Repubblica noted, however, while the debate was "harsh" and "characterized by low blows from both sides," neither candidate had landed "the knockout blow."
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