Acrid bitterness inevitably seeps into the lives of people who harbor grudges and suppress anger, and bitterness is always a poison. It keeps your pain alive instead of letting you deal with it and get beyond it. Bitterness sentences you to relive the hurt over and over.
Courage would be impossible in a world without pain.
Moral evil is the immorality and pain and suffering and tragedy that come because we choose to be selfish, arrogant, uncaring, hateful and abusive.
There are Eastern religions that deny the reality of pain and suffering. They just try to wipe it away by saying it's all an illusion.
It is very difficult to give a 15 second sound bite on why there is pain and suffering in this world and not have it come off as being flippant or surface level or superficial.