"Nuclear proliferation is the biggest risk mankind faces," said Dimon, head of the largest U.S. bank and the world's largest investment bank by revenue. According to him, the West has to have clarity and subordinate many things "to make sure that this ends up right."Dimon has described himself as a supporter of Ukraine, and JPMorgan Chase has been involved in Ukraine's recovery efforts. Along with another U.S. investment firm, BlackRock, the company agreed to set up a $15 billion fund for Ukraine. "A lot of other nations that border Russia, they're quite worried. And some of (those who) don't border Russia are quite worried," he said."And we have never had a situation where a man is threatening nuclear blackmail, 'if your military starts to win, we are rolling out the nuclear weapons' type of thing.