I give you the Crusades from 1095 to 1291 AD for length and deaths.  

I give you the Islamic Jihads of Shia vs Sunni since the death of Muhammed and continuing  in Syria on this very day.

Some conflicts fought as jihad since the 1980s include:
Iran–Iraq War (1980–88, considered a jihad by the Islamic Republic of Iran)[165]
Kashmir conflict (Lashkar-e-Taiba, 1990–present)
Somali Civil War (1991–present)
Afghan civil war (Taliban 1994–present)
East Turkestan irredentism (East Turkestan Islamic Movement, 1997–present)
Chechen war and Insurgency in the North Caucasus (Arab Mujahideen in Chechnya, 1994–present)
Nigerian Sharia conflict (Boko Haram 2001–present)
Iraqi insurgency (Islamic State of Iraq, 2003–present)
Al-Qaeda insurgency in Yemen (Abyan Governorate, 2010–present)
Syrian civil war (Al-Nusra Front, 2011–present)

I give you Northern Ireland;  I give you the "30 -Years War" where "Christians" fought Catholics. from 1618 to 1648.

Death and Religion are inseparable!