Erica Chenoweth initially thought that only violent protests were effective. However after analyzing 323 movements the results were opposite of what Erica thought:
For the next two years, Chenoweth and Stephan collected data on all violent and nonviolent campaigns from 1900 to 2006 that resulted in the overthrow of a government or in territorial liberation. They created a data set of 323 mass actions. Chenoweth analyzed nearly 160 variables related to success criteria, participant categories, state capacity, and more. The results turned her earlier paradigm on its head — in the aggregate, nonviolent civil resistance was far more effective in producing change.
If campaigns allow their repression to throw the movement into total disarray or they use it as a pretext to militarize their campaign, then they’re essentially co-signing what the regime wants — for the resisters to play on its own playing field. And they’re probably going to get totally crushed.
Every US protest which involved violence that I have looked into except one started peaceful and only became violent because of police starting the violence, provoking protestors to defend themselves by forcing them into dangerous situations, or police overreacting to instigators and agitators.
The only one where the protestors were the ones who instigated violence that I have come across was the Jan 6th insurrection. There could be more, but that is the only one I have found.
Of course civil resistance that doesn’t end up with violence will be more successful. It is a lot harder to demonize protestors who didn’t have to defend their lives when you can’t pretend they were the violent ones.