Green’s Dictionary of Slang

1. wonderful, excellent, admirable.

1954		W. Chasen ‘Teen-age Gang From the Inside’ in N.Y. Times Mag. Mar 21 17: the gang boy’s model of success is the man ‘with lots of bread’ who rolls through the neighborhood in a ‘vicious’ convertible, stopping here and there to transact his business—women, numbers and narcotics.
1979		Sugar Hill Gang ‘Rapper’s Delight’ 🎵 She’s heard stories and she’s heard fables / That I’m vicious on the mike and on the turntable.
1989		P. Munro Sl. U.
1999		Guardian Friday Rev. 11 June 14: And he clicks his hand with vicious cool.
2002		‘Valley Girls’ on Paranoiafanzine 🌐 And I’ll even show you how to be a maximum warm babe like us how to get a totally viscious [sic] dude to notice you.

2. serious.

1989

(con. 1982–6) T. Williams Cocaine Kids (1990) 18: I know I fucked up and made some vicious mistakes when I was behind the scale.