The adjective contentious means something that involves or is likely to cause disagreement.

Synonyms are antagonistic, combative, quarrelsome, or testy.

The word origins from Latin (early 15th century) contentious meaning “obstinate, quarrelsome”, from contentionem meaning “a vigorous struggling, a contest, a fight”. It also comes from the past participle stem of contendere.

He has some very contentious friends in school

The coach had a contentious relationship with the tennis player.

Do not open a contentious topic in the discussion.