Nastier rhymes with:
rustier, tastier, altier, carpentier, cartier, chartier, cloutier, cottier, courtier, dirtier, emptier, flightier, fortier, gautier, heartier, heftier, loftier, meatier, meteor, mightier, mintier, mortier, palmatier, parmentier, peltier, portier, potier, prettier, rustier, saltier, sportier, tastier, thriftier, trottier, whittier
Nastier sounds like:
nectar, negotiator, nester, nestor, neumeister, newscaster, nicastro, nichter, nicotera, nicotra, nighter, non-sequitor, nostra