In at least two places in the NT the Bible states that those who killed Jesus were not aware of their sin in doing so. I wonder how most would compare the sinfulness of crucifying Jesus with that of present day terrorists. I raise that issue because I often hear someone state that the actions of this or that terrorist group are so evil that they are beyond the pale, proving without a doubt that the perpetrators are willfully and totally evil. In considering these remarks I hark back to the words of Jesus on the cross: Forgive them for they know not what they do. Then we also see the words of Peter in Acts 3:17 in which he said those who killed Jesus did so in ignorance. In both instances the Bible exonerates the killers from the idea of willful evil. In fact, the Bible seemingly confirms that those who participated in Jesus' death thought they were doing what was right and good. They were not driven by a desire to be as evil as possible; they erroneously thought that, by killing a man they saw as a dire threat, they could do the greater good, much as we often think today.
Maybe many Christians believe that the atrocities of ISIS and others exceed the sinfulness of killing Jesus, but certainly the mistreatment of Jesus should rank high on the sinfulness list of those who want to grade sins. If the sin of crucifying the Son of God was committed in ignorance, then we needn't assume that other horrendous acts are not similarly motivated by ignorance.
Of course, the fact that evil is done in ignorance does not mitigate its impact and the associated suffering. But it does bring into question all the mental gymnastics which allow us to engage in" reciprocal" evil and feel perfectly justified and righteous in doing so.