There was no altruistic motive that prompted him to help her.

Altruistic : showing a disinterested and selfless concern for the well-being of others; unselfish.
Wicked : evil or morally wrong.
Brutal : savagely violent.
Inhuman : lacking human qualities of compassion and mercy; cruel and barbaric.
Selfish : (of a person, action, or motive) lacking consideration for other people; concerned chiefly with one's own personal profit or pleasure.

Antonym of Altruistic is Selfish