The phrase is everyday French vulgar slang, where 'baiser' is used crudely and 'un max' means to the maximum, so the whole line works as an exaggerated compliment. Short French voice clips like this spread on soundboards and in meme edits because they need no context and translate instantly through tone alone, even for viewers who do not speak French. It has stayed popular as a reaction sound for reveals, transformations and moments that are meant to look irresistibly good, with the shock value of the wording adding extra comic impact.