Oh you sweet summer child. Humans are one of the most amicable creatures on the planet.
Normal bear behavior
Large mammals, like bears or lions, routinely kill the young of their own kind if they come across them. Not out of malice or anything, if the cubs die the female becomes fertile again and will take their seed. Procreation of your own genes is paramount and many mammals practice infanticide just to make more room for their own young.
Chimpanzees are even worse. Beasts only kill the young to further their seed. Chimps wage total war of extermination against other chimpanzee groups. Their wars can go on for years and engage both males and females as combatants, although females are usually raped into submission and assimilated. Our closest cousins make Silastic Armorfiends of Striterax look tame by comparison.
Dolphins are some of the nicest creatures imaginable. They don’t wage war against other dolphins, but merely form rape-packs of adult males who prowl the seas, looking for females to gang-rape. Sometimes they drown females that way.
Modern humans are actually quite docile and agreeable by mammalian standards. Stone age was a bit different, but now we at least make an effort to prosecute rape and don’t consider child-killing and wars of extermination as acceptable. We still do them on occasion sure, but we don’t endorse them like most of our relatives do.
In HFY terms, Earth is a Class IV Deathworld – a fully developed Cannibal world and we’re on top of that.