Brittlest rhymes with:
anti-federalist, bicyclist, colonialist, criminalist, cyclist, dualist, duelist, editorialist, environmentalist, experimentalist, fatalist, federalist, finalist, fundamentalist, gaullist, generalist, gradualist, idealist, imperialist, individualist, industrialist, instrumentalist, internationalist, loyalist, materialist, medalist, mercantilist, minimalist, moralist, motorcyclist, noblest, philatelist, presidentialist, pugilist, realist, revivalist, royalist, semifinalist, sensationalist, spiritualist, stylist, survivalist, tallest, traditionalist, vocalist, zimbalist