Qu’ranic references about violence

And prepare against them whatever you are able of power and of steeds of war by which you may terrify the enemy of Allah and your enemy (Surah Al-Anfal v 60)
(the action of killing without justification is categorically rejected in another verse)
….whoever kills a soul unless for a soul or for corruption [done] in the land – it is as if he had slain mankind entirely. And whoever saves one – it is as if he had saved mankind entirely. (Surah Al-Ma’idah v 32)
(On the other hand, recourse to killing is possible in justifiable circumstances according to the following verse):
Indeed, the penalty for those who wage war against Allah and His Messenger and strive upon earth [to cause] corruption is none but that they be killed or crucified or that their hands and feet be cut off from opposite sides or that they be exiled from the land. That is for them a disgrace in this world; and for them in the Hereafter is a great punishment, (Surah Al-Ma’idah v 33)