Moscow (AFP) – Russian President Vladimir Putin on Thursday mocked Joe Biden for calling him a “killer” — saying “it takes one to know one” — as ties between Moscow and Washington sank to new lows. US President Biden’s comments sparked the biggest crisis between Russia and the United States in years, with Moscow recalling its ambassador for consultations and warning that ties were on the brink of outright “collapse”. But speaking during an event marking seven years since Russia’s annexation of Crimea, Putin ruled out severing ties with the United States altogether and lobbed a jab at the 78-…