Huge, vast, immense, enormous, elephantine, mammoth, giant, gigantic, gigantean, colossal, gargantuan, Herculean, cyclopean, titanic, Brobdingnagian are comparable when meaning exceedingly or excessively large.
Huge is a rather general term indicating extreme largeness, usually in size, bulk, or capacity.
Vast denotes extreme largeness or broadness, especially of extent or range.
Immense suggests size far in excess of ordinary measurements or accustomed concepts.
Enormous also indicates a size or degree exceeding accustomed bounds or norms.
Elephantine suggests the cumbersome or ponderous largeness of the elephant.
Mammoth is similar to elephantine.
Giant indicates unusual size or scope.
Gigantic and the uncommon gigantean are close synonyms of giant perhaps more likely to be used in metaphorical extensions.
Colossal may suggest vast proportion.
Gargantuan suggests the hugeness of Rabelais’s Gargantua and is often used in reference to appetites and similar physical matters.
Herculean suggests the superhuman power of the Greek hero Hercules or the superhuman difficulties of his famous labors.
Cyclopean suggests the superhuman size and strength of the Cyclops of Greek mythology.
Titanic suggests colossal size and, often, primitive earth-shaking strength.
Brobdingnagian suggests the hugeness of the inhabitants of the Brobdingnag of Gulliver’s Travels.