Of course they can be cruel, but not as crual as men to create massive destruction among others. Fish are quite similar, because in most of the cases they attack each 'race' or however you call it.
I could write about good things people do for hours, that's for sure, but the bad things are just as long. In fact, when you think about (bad/evil) stuff that people do, it's quite horrible.
Sure, a newly developed brain & amygdala can bring out brilliance, but the same brain and creative side of it also created bombs and sickness (given by bombings and depleted uranium) that not even new medicine, which the 'good brain' created, can't cure.
I think there's an ounce of good and an ounce of evil in every human being ever since the birth. And it's to the prenatal period, parenthood and society to shape it up. Surely, an individual is also who makes the difference to decide which path to take. Humans are much more complicated too, due to more developed brain and emapthy that animals generally lack.