VATICAN CITY — Pope Francis on Sunday appealed to Russian President Vladimir Putin for a cease-fire, imploring him to “stop this spiral of violence and death” in Ukraine and denouncing the “absurd” risk of the “uncontrollable” consequences of nuclear attack as tensions sharply escalate over the war. Francis uttered his strongest plea yet about the seventh-month-old conflict, which he denounced as an “error and a horror.” It was the first time in public that he cited Putin’s role in the war. The pontiff also called on Ukrainian President Volodymyr Zelensky to “be open” to serious peace proposals. Francis told the...