【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.