VILLAINOUS
nefarious, villainous
(adjective) extremely wicked; “nefarious schemes”; “a villainous plot”; “a villainous band of thieves”
Source: WordNet® 3.1
Etymology
Adjective
villainous (comparative more villainous, superlative most villainous)
Of, relating to, or appropriate to a villain.
Wicked, offensive, or reprehensible in nature or behaviour; nefarious.
Source: Wiktionary
Vil"lain*ous, a. Etym: [Written also villanous.]
1. Base; vile; mean; depraved; as, a villainous person or wretch.
2. Proceeding from, or showing, extreme depravity; suited to a
villain; as, a villainous action.
3. Sorry; mean; mischievous; -- in a familiar sense. "A villainous
trick of thine eye." Shak. Villainous judgment (O. E. Law), a
judgment that casts reproach on the guilty person. ---
Vil"lain*ous*ly, adv. Vil"lain*ous*ness, n.
Source: Webster’s Unabridged Dictionary 1913 Edition