Tony/Bush killed 100s of thousands aggressively.
Obama administration killed thousands silently.
Mao Tse-Tung in China Killed 45 millions
Joseph Stalin in USSR killed almost 20 million in which 14.5 m were starved to death.
Benito Mussolini - Over 400,000 italians were killed during his era

We bring religion when it comes to violence but if you do proper analysis the main reason behind mass killings are politics and nationalism. Religion is very simple, have faith on the uncreated cause of the universe and be good and do good, as simple as that.