It is grudge(恨) and attachment(愛着) that causes the greatest damage to humans in their life.
Grudge comes into being when their ignorance about what exists has them deceived by themselves or other people. Attachment is formed when they tie their mind to useless things that cannot be achieved.
Grudge and attachment are the things that humans must be vigilant against. What we need to think about most importantly is that whether or not we come to possess grudge by being deceived and whether or not our ignorance has our mind bound to useless things so we wander around in the darkness through life and death.