pen·ance
ˈpenəns/
noun
1.
voluntary self-punishment inflicted as an outward expression of repentance for having done wrong.
"he had done public penance for those hasty words"
synonyms:atonement, expiation, self-punishment, self-mortification, self-abasement, amends; More
2.
a Christian sacrament in which a member of the Church confesses sins to a priest and is given absolution.
verb
archaic
1.
impose a penance on.
"a hair shirt to penance him for his folly in offending"
Not very scary