Formal:
* Incroyable: This is the most common and literal translation, and it is generally considered formal.
* Extraordinaire: This means "extraordinary" and can also be used to express something incredible.
Informal:
* Génial: This is a more casual way to say "incredible," meaning something awesome or great.
* Fantastique: This means "fantastic" and can also be used for something incredible.
* Super: This is a very informal and common way to say "incredible," meaning something great or cool.
Other possibilities:
* Inouï: This means "unheard of" and can be used to describe something truly incredible.
* Remarquable: This means "remarkable" and can be used for something impressive or extraordinary.
Here are some examples of how these translations can be used:
* "C'est incroyable!" (That's incredible!)
* "Le spectacle était extraordinaire." (The show was extraordinary.)
* "Ce film est génial!" (This movie is awesome!)
* "Le concert était fantastique." (The concert was fantastic.)
* "Le gâteau est super !" (The cake is great!)
The best translation will depend on the specific context and the level of formality you want to convey.