"hugest" grammatically correct? [closed]

Yes, huge sounds like an absolute adjective, but the following dictionary entry explicitly allows both comparative and superlative forms for huge:

Huge adjective (huger, hugest) 1 Extremely large; enormous - ODO

This Ngram comparing huge/hugest with large/largest appears to show that the relative usage of the respective superlative forms are roughly proportional. But in reality, as Peter Shor notes with a much clearer Ngram, the usage of hugest vs huge is tiny compared with the usage of largest vs large.

This confirms the subjective assessment that hugest isn't used much. Here's an Ngram comparing hugest with an antonym of sorts, pyknic (short and fat), and ventripotent (big-bellied) showing that there are indeed real words that are currently less used than hugest.