Negate

deny oppose cancel refute negative reverse invalidate nullify rescind repeal abrogate annul gainsay traverse abate neutralize undo quash retract countermand frustrate disprove controvert impugn disallow revoke vitiate belie redress kill put down dump annihilate break with cancel out countercheck cross ding disaffirm fly in the face of stonewall turn down turn thumbs down void blackball