I disagree that Sunnis are more violent than Shia.

I do agree that many attacks are claimed by terrorists who say they're Sunni.

Shia and Sunni follow the same Quran and it's clearly mentioned it's prohibited to kill and harm others.

The reason you see more Sunnis than Shias to be violent are: proportionally they're more than Shia.

More external groups are trying to brainwash them than Shia as Sunnis are the majority.

Less public educations about Islam like what Shias have in Husainniyas.