Forget all the worst atrocities. Think about average people going about their daily lives.
It's the weekend. You go out and buy some food, some treats, a bottle of wine, some ice tea, some coffee, a new pair of jeans, you have an ice cream, etc. You could drink tap water. You could eat only rice with lentils. You could wear that old pair of trousers, even though they have a hole in them. That would have saved you 100 bucks.
You could have donated that 100 bucks to a charity that saved a child's life. We all know that 100 dollars goes a long way in the third world. Instead we choose to spend that money on luxuries. You could have volunteered at a local charity. Instead you chose to go shopping. If you saw some kid drowning in a puddle, watched the kid die a preventable death as you were eating an ice cream, that would be evil. We all do that on a daily basis. We know our choices cause suffering, but because that suffering happens far away and we don't get to see it happen, we happily ignore it. That's everyone. Some of us are "I'll sometimes buy an ice cream and let a baby cow get turned into pate" evil. Some of us are "I'll buy gold toilets while a hundred kids die." evil. But arguably no one is actually good.
I think the only way to forgive ourselves for our constant daily selfishness and depravity, is to accept that humans aren't that special. We're evolved primates. We are animals who act on instinct and lack the empathy or intelligence to ever become truly moral. You might as well expect a jelly fish to sing a ballad. It is not in our nature to become anything better than what we are.