Definition of monstrous :
1. Abounding in monsters.
2. Exceedingly; very; very much.
3. Extraordinary in a way to excite wonder, dislike, apprehension, etc.; - said of size, appearance, color, sound, etc.; as, a monstrous height; a monstrous ox; a monstrous story.
4. Extraordinary on account of ugliness, viciousness, or wickedness; hateful; horrible; dreadful.
5. Having the qualities of a monster; deviating greatly from the natural form or character; abnormal; as, a monstrous birth.
6. Marvelous; strange.
mega, hateful, chimerical, fantastical, awful, mighty, right, grave, enormous, massy, false, unattractive, Herculean, horrendous, deformed, serious, fantastic, whopping, unpleasing, outrageous, unhandsome, titanic, planetary, homely, grisly, nightmarish, elephantine, colossal, horrid, frightful, irrational, gigantic, Himalayan, oceanic, leviathan, pythonic, scandalous, abnormal, ill-advised, ghastly, dangerous, nonsensical, unsightly, life-threatening, appalling, humongous, uncharitable, painful, mammoth, ludicrous, whacking, vasty, gigantesque, ill-judged, mountainous, ugly, incorrect, immense, weighty, inhuman, grievous, unpretty, monster, super, large, grotesque, galactic, ill-considered, stupid, senseless, king-size, astronomical, plain, shocking, Cyclopean, gruesome, heartrending, unreasonable, wild, antic, terrific, vile, misshapen, heartbreaking, prodigious, mastodonic, hard, unkind, absurd, unlovely, stupendous, ridiculous, cosmic, pharaonic, erroneous, tremendous, monumental, anomalous, bumper, preposterous, grand, inconclusive, paradoxical, unnatural, behemoth, heroic, freakish, nightmare, ill-favored, lurid, grim, horrible, cruel, distorted, giant, walloping, mistaken, infatuated, severe, uncanny, macabre, unbeautiful, gargantuan, uncomely, freaky, horrifying, dreadful, super-duper, supersized, Bunyanesque, massive, shapeless, vast, horrific, pitiless, foolish, flagitious, unusual, heavy, Brobdingnagian, unspeakable, jumbo, huge, big, supersize, usual, unappealing
evil (part of speech: adjective)
disgraceful, offensive, sinful, repugnant, terrible, detrimental, calamitous, loathsome, revolting, abominable, sinister, foul, nefarious, evil, bad, repellent, damnable, repulsive, hideous, destructive, heinous, wicked, baneful, atrocious, reprehensible
- When I came here three years ago he had not yet done any of these things- publicly; these perfectly monstrous things. - "The Case of Richard Meynell", Mrs. Humphrey Ward.
- Under the name of fashion and art much is done in society that would be simply monstrous on ordinary occasions. - "Barriers Burned Away", E. P. Roe.
- The mere suspicion was a monstrous wrong! - "The Just and the Unjust", Vaughan Kester.