Directly opposing the idea of fairness:
* Cheating: This directly opposes the idea of playing by the rules.
* Unfairness: This is a more general term for the absence of fairness.
* Dishonesty: This refers to a lack of integrity and truthfulness.
Opposing the idea of playing by the rules:
* Rule-breaking: This refers to deliberately violating established rules.
* Foul play: This refers to actions that are illegal or unethical in a particular game or activity.
* Underhanded tactics: This implies using deceitful or unethical methods to gain an advantage.
Opposing the idea of sportsmanship:
* Bad sportsmanship: This refers to unsportsmanlike conduct, such as taunting opponents or refusing to shake hands after a match.
* Ruthlessness: This describes a lack of empathy or compassion for opponents.
* Aggression: This can refer to excessive physical or verbal hostility.
Ultimately, the best opposite for "fair play" depends on the specific context and what you want to emphasize.