We do not currently know of any antonyms for absolute superlative.
The noun absolute superlative is defined as:
In Italian, Spanish, Portuguese, and Catalan: the form of an adjective formed by adding the suffixes -issimo, -isimo, -íssimo, -érrimo, -imo, or -íssim to the adjective (with any final vowel dropped) to express a superlative that cannot be exceeded, having the sense “as... as possible”.