Which shows the greatest conflict between different groups of Christians ?

major conflict of Christianity?:

Christians have held diverse views towards violence and non-violence through time. Currently and historically there have been four views and practices within Christianity toward violence and war: non-resistance, Christian pacifism, just war, and preventive war (Holy war, e.g., the Crusades).

I don't know if this is what you're looking for but this is what i found

because the vietnam war was fought in an especially brutal and untraditional way