Remorse (noun)

1. Deep regret or guilt for a wrong or misdeed.
2. The action of feeling such regret or guilt.

Origin:

Late middle english: from old french remors, based on latin remordere "bite again", from re- "again" + mordere "to bite".

Examples:

1. He felt remorse for what he had done.
2. She expressed remorse for her actions.
3. He had no remorse for the harm he caused.
4. The criminal showed remorse for his crime.
5. The soldier felt remorse for what he had to do during the war.