Sternest rhymes with:
ernest, abolitionist, accompanist, antagonist, arsonist, botanist, calvinist, cartoonist, chauvinist, cleanest, columnist, communist, conservationist, contortionist, determinist, dishonest, ernest, exhibitionist, expressionist, feminist, finest, gymnast, harnessed, honest, illusionist, impressionist, isolationist, jansenist, keenest, kienast, leanest, machinist, meanest, menaced, modernist, neoplatonist, obstructionist, organist, perfectionist, pianist, platonist, protagonist, soonest, unionist, violinist, witnessed
Sternest sounds like:
southernmost, stormiest, strangest, strength, stringed, stromquist, strongest