English has many words for 'big', but they carry different intensity. Which one means shockingly, overwhelmingly huge?

"Colossal" describes something so enormous it inspires awe or shock, a stronger intensity than everyday words for size, and it derives from the Colossus of Rhodes, an ancient bronze statue so massive it became legendary for its scale. Using it signals the speaker wants to emphasize extremity, not just note that something is big.

"Large" is a plain, neutral size descriptor with no emotional charge, and "decent" actually suggests something modest or adequate rather than impressively big — both fall far short of the overwhelming scale "colossal" conveys.

English has several size words borrowed from legendary giants and monuments this way — "gigantic" nods to the mythical Giants, and "titanic" comes from the Titans of Greek myth, both following the same pattern as "colossal."