People who are completely different make ideal partners.

(idiomatic) A person who holds a position in an organization that corresponds to that held by another person in another organization; a counterpart

Women in relation to men or men in relation to women. / (attributively) Heterosexual, or otherwise relating to a relationship between a woman and a man.

plural of Leader of the Opposition

(politics, UK) In a house of legislature following the model of the Westminster system (such as the UK House of Commons), the parliamentary leader of the largest political party not forming the government.

plural of polar opposite

plural of opposite number

(politics, sometimes attributive) The force acting against the opposition.

The team in a British Parliamentary Style debate which gets the second and fourth speech (of a total of eight).

The team in a British Parliamentary Style debate which gets the sixth and eighth (last) speech.