The Oxford Dictionary gives the comparative and superlative forms of chic as chicer and chicest. 

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These are wholly English words: the French equivalents would be plus chic and le/la plus chic. Super-chic is sometimes used: "super-chic Incline bucket in mouth-blown, moulded glass".^[4]

An adverb chicly has also appeared: "Pamela Gross ... turned up chicly dressed down".^[5]

The use of the French très chic (very chic) by an English speaker – "Luckily it's très chic to be neurotic in New York"^[6] – is usually rather pretentious, but sometimes merely facetious—Micky Dolenz ofThe Monkees described ironically the Indian-style suit he wore at the Monterey Pop Festival in 1967 as "très chic".^[7] Über-chic is roughly the mock-German equivalent: "Like his clubs, it's super-modern, über-chic, yet still comfortable". ^[8]