The genocide of the Catholic Nazi state in Croatia in WW2. Christian Arabs carried out appalling massacres in the 1970s-80s Lebanon War, including the Sabra and Shatila massacre of 1982. 1990s Serb Orthodox genocide. Late 20th century Protestant death squads in Ireland.
See also:
The 1994 Rwandan genocide was committed by Christians (Rwanda is 90 percent Christian). In Rwanda, Islam means peace, Christianity means hate The Cross and the Genocide - Notes that Rome has refused to excommunicate Catholics involved in the genocide - just as they refused to excommunicate Catholics involved in the Holocaust. As it sheltered Nazi and Croat war criminals after WW2, so the Vatican sheltered war criminal Fr. Athanase Seromba for months after the Rwandan genocide. War criminals still hiding, Jon Swain, Sunday Times, Aug 13, 2006 - The Vatican is believed to be still sheltering other war criminals. In Zimbabwe, the marxist-authoritarian Mugabe is also Catholic, and his murderous regime has long been protected by the Zimbabwe Catholic church. Excommunicate Mugabe - Tony Allwright says in 2006: "in permitting Mr Mugabe to remain a Catholic, the Pope is demeaning the whole Church". If only more Catholics were like him. If only the Catholic hierarchy stood up for human rights internationally, and clearly differentiated between good and evil. Mugabe in Rome for beatification of Pope John Paul II, 30 Apr 2011. Uganda is 85 percent Christian The mass murderers and rapists the Lord's Resistance Army. Christian sharia law in Uganda - The death penalty for homosexuality proposed 2009. Islamists praise Uganda for proposing death for gays. The fascist Ugandan newspaper Rolling Stone calls for death for gays. The U.S. magazine Rolling Stone is horrified at these creeps using their name. The killing of David Kato, Jan 2011, was apparently nothing to do with the Rolling Stone campaign. Central African Republic conflict (2012 on)
Just because they're in Africa, doesn't mean they aren't real Christians.
From here: http://markhumphrys.com/christianity.killings.html