Cynic

1. a person who believes that only selfishness motivates human actions and who disbelieves in or minimizes selfless acts or disinterested points of view.

2. ( initial capital letter ) one of a sect of Greek philosophers, 4th century b.c., who advocated the doctrines that virtue is the only good, that the essence of virtue is self-control, and that surrender to any external influence is beneath human dignity.

3. a person who shows or expresses a bitterly or sneeringly cynical  attitude.