Several express concern at Mr Trump's claim that the election will be rigged and at his threat that he may refuse to accept the outcome if he loses.
These concerns are summed up succinctly by a headline in France's Le Point: "Trump can no longer win, but can refuse to admit defeat".
Spain's El Mundo says that Mr Trump's aggressive attitude during the debate "once again made Clinton a winner 'by default' over her rival".
The paper adds that Mr Trump's suggestion that he could refuse to accept the election result is likely to overshadow the remaining days of the campaign, and predicts that his remark will not help his cause.
'One step away from the abyss'
Massimo Gaggi comments in Italy's Corriere Della Sera that Mr Trump is now "one step away from the abyss".
Mr Gaggi writes that it had earlier seemed that Mr Trump could not do his campaign any more harm. However, "on Wednesday night Trump managed it, openly threatening to provoke an institutional crisis without precedent by refusing to accept defeat if Hillary beats him".
In Germany, Christoph von Marschall writes in Berlin's Tagesspiegel that "We are used to such things... from states with authoritarian governments. But not from western democracies!"
He is in no doubt over who emerged as the winner of the debate: "Trump is not an equal partner when it comes to objective argument. He can only curse and rant - and dole out insults."
'Democracy under attack'
The pattern is repeated in the Middle Eastern press, with many papers seeing Mrs Clinton as now having a clear lead over her rival.
The UAE's Al-Bayan daily says that "Clinton surpasses Trump", while the Libyan news website Al-Mostakbal declares: "Clinton ahead of Trump three weeks before elections".
A commentary by Hesham Melhom in Lebanon's Al-Nahar focuses on Trump's "unfounded" allegations that elections will be rigged against him: "Trump is trying to prepare himself for losing, intimidate the Democrats and spread a climate of tension to dissuade voters from going to the polls".
Boaz Bismuth writes in the Israeli daily Yisrael Hayom: "There is no doubt that the road to the White House today seems easier for Hillary Clinton."
However, a gloomy analysis in the left-of-centre Israeli broadsheet Ha'aretz says that even if Trump is heavily defeated in the election, "the darkness is already here... liberal democracy is under attack."
The Russian business channel RBC TV says the debate "was again won by Hillary Clinton", an opinion shared by the Gazeta.ru news website.
"Clinton demonstrated her iron self-control", it writes. "Trump... lost all his energy. He kept silent more often and attacked less."
The pro-Kremlin business website Expert Online thinks the two candidates fought a draw: "A great majority of polls still show that Clinton is beating Trump... But Trump is obviously winning on social networks."
Russian TV station, Rossiya 24, focuses on the mention of President Putin: "It took Hillary Clinton less than 30 minutes to once again accuse Russia of committing cyber attacks against the USA and Donald Trump of liking the Russian leader", it reports.
China's Global Times says that the candidates' final encounter "looked more like a fight than a debate" .