Antithetical

[Tanya Shivari]

Pertaining to antithesis, or opposition of words and
sentiments; containing, or of the nature of, antithesis; contrasted.

[Tina]

Opposed to an [idea].

[Little_Girl]

Contradictory; achieving [antithesis]; containing opposites. [Honestly], a word that people only use when they want to [seem] smart.

[Greta]

Directly opposed or contrasted; mutually incompatible.

[Michiko]

exactly the opposite of someone or something or of each other: