Unpleasant, dreadful, awful (also used as an intensifier).
Genuinely horrific, awful, or alarming.
Frightfully; very.
Spiteful, unkind.
Grave or dangerous (of an accident, illness etc.).
Contemptible, unpleasant (of a person).
Awkward, difficult to navigate; dangerous.
Dirty, filthy.
Indecent or offensive; obscene, lewd.
Formidable, terrific; wicked.
Objectionable, unpleasant (of a thing); repellent, offensive.
Sexual intercourse.
Something nasty.
A video nasty.