Prefix: counter- (Latin)

counterpoint

(n) A contrasting item, opposite; a complement; the use of contrast or interplay in a work of art

counterfeit

(n.) an imitation designed to deceive; (adj.) not genuine, fake; (v.) to make an illegal copy

Counterculture

A culture with lifestyles and values opposed to those of the established culture

counterblast

A defiant or aggressive response to a verbal attack

counterprotest

A protest held in opposition to another protest

counterbalance

A weight used to balance an opposite weight

counterproposal

Amends the terms and conditions of a proposed contract to buy/sell

countermeasure

An action taken against a threat or other unwanted action

counterblock

An action undertaken to break through or subvert a blockade

counterattack

An attack made in response to an enemy's attack

counterintuitive

Going against intuition (going against gut feeling or common sense)

counterproductive

Having the opposite of the desired effect

counter-

Latin prefix meaning "against, in opposition to"

counterfactual

Relating to or expressing what has not happened or is not the case

counteract

To act against, neutralize, or make ineffective

counteraccusation

an accusation made in turn by someone against their accuser

counterclockwise

in the direction that is opposite of the direction the hands on the clock move