Green’s Dictionary of Slang

badly, rottenly.

2001		OnLine Dict. of Playground Sl. 🌐 vrot, Rotten. eg: ‘We all got fucked up vrot yesterday.’.
2011		(ref. to c.1985) Mail & Guardian (Johannesburg) 23 Apr. 🌐 I remember going into a police station [...] ion the miod-80s, and the man in charge complaining that the black woman‘praat vrot Afrikaans’.