General meaning:
* Contraire: This is the most common and direct translation. It can be used as an adjective, noun, or adverb.
* Opposé: This means "opposed" and is often used in the context of opposing ideas or arguments.
In the sense of "on the contrary":
* Au contraire: This is the most common way to express "on the contrary".
* Bien au contraire: This is a more emphatic way of saying "on the contrary".
In the sense of "despite" or "in spite of":
* Malgré: This means "despite" or "in spite of" and can be used to introduce a contrary idea.
Examples:
* C'est le contraire de ce que j'ai dit. (This is the contrary of what I said.)
* J'ai entendu dire qu'il pleuvait, mais au contraire, il fait beau. (I heard it was raining, but on the contrary, it's sunny.)
* Il est parti malgré mon opposition. (He left despite my opposition.)
The best translation will depend on the specific context of your sentence.