The pontiff topped Sen. Ted Cruz, who was number five on Time magazine's list.
Kerry said the people of Ukraine "deserve better."
He said a deal ending enrichment "was on the table a hundred years ago" but "has been lost."
The president’s handshake with Cuban President Raúl Castro provoked disapproval from GOP.
Washington's top diplomat in Afghanistan told Congress that President Hamid Karzai is playing a dangerous game in stonewalling a postwar pact, reiterating the Obama administration remains willing to pull all forces out of the country next year.
"Can imagine what Nelson Mandela would say," Leahy tweeted.
McConnell criticized Reid for pushing the Defense authorization bill without amendments.
The leading Cuba hawk in Congress slammed Obama for shaking the Cuban leader's hand.
A bipartisan group of House members has proposed a resolution honoring the life of Nelson Mandela, the anti-apartheid icon and former South African president who died last week.
McCain later said he was joking, although the gesture "was terrible."