enormous, huge, massive, vast, very great, tremendous, substantial, goodly, prodigious, gigantic, giant, terrific, fantastic, colossal, immense, mammoth, monumental, stupendous, gargantuan, elephantine, titanic, mountainous, monstrous

extremely, very, really, thoroughly, exceedingly, immensely, incredibly, amazingly, remarkably, exceptionally, uncommonly, extraordinarily, perfectly, truly, simply, positive, positively, downright