Christianity has, historically, been the more violent religion.
Which one now do you consider more violent?
It's kind of a loaded question without a clear answer.
Christians are just a violent as muslims, they just found other things they like killing for more than religion (money, oil, power). Muslim countries are, in general, being attacked or suppressed by christian countries (for their oil, money etc). Those muslims then need to try to find ways to defend themselves. Many of them frame that defense in religious terms. Thus a war that is actually about colonialism and greed turns into a holy war.
So you will find muslims that justify their actions with religion, while christians (who are doing similar shitty stuff) don't frame it as religiously based.
So if you want to take a super simplistic way of looking at it, you could say Islam is more violent since some muslims claim to be fighting for their religion and Christianity is less violent because Christians just kill for money. But Christians are still killing more muslims than muslims are christians. Trying to frame it as which religion is more violent is just an inherently useless question. Both sides are fighting for power and wealth, one side just uses religion to frame their actions and the other doesn't.