Factions aren't limited to Christianity, by any means. Islam's two major factions absolutely hate each other. And it's particularly odd, because they only seriously differ on two points (both of which refer to who is allowed to lead them).
Judaism has sects, but they don't really hate each other. But that's because the most orthodox groups don't see the reform groups as heretics, per se. More like they are just no longer Jewish in their eyes. They aren't really "Conver to my religion or GTFO" people. More like "You want to convert to my religion? GTFO."
1200-1500 Italy, in particular, are heinous when it comes to Christian sects warring. This was a time when they were ALL CATHOLIC, but they would burn monks at the stake as heretics for the stupidest reasons (like believing that clergy should be poor or rich--both sides killed the other). There were points when they actually had multiple popes, and multiple leaders for the Holy Roman Empire--it's absurd.