Damnation is the act of damning, which is a lot like condemning. Damnation dooms people.
In many religious traditions, when someone is damned, it means they are doomed to suffer horribly in hell forever. Damnation, therefore, is the action of sending someone to hell. However, this word can refer to other forms of being condemned. Being sentenced to prison is a type of damnation. Being disgraced in public is a type of damnation. Anything that dooms you is damnation of a sort. Often, damnation comes from our own actions.