Well Atheism is only really a new religion so it's got a ways to go yet. But certainly the militant atheists are annoying enough to make one want to blow one's self up... if that counts.
But Christians had the crusades, Muslims had 9/11, I'm sure the Atheists will have some sort of mass killing period in the future.
A poster of some consequence...
The most dangerous military stratagem was organised by King Goujian of Yue (present-day Shanghai, northern Zhejiang and southern Jiangsu) in 496 BC. King Goujian's army was known for forcing their front line, composed of criminals sentenced to death, to commit suicide by decapitating themselves to scare their enemy before battle. If they refused their whole family was killed.
I watched with glee, while your kings and queens, fought for ten decades for the gods they made.