Saddest rhymes with:
blondest, buddhist, coldest, eldest, encyclopedist, fondest, grandest, hardest, kindest, loudest, methodist, mildest, modest, oddest, oldest, orthopedist, prejudiced, propagandist, proudest, rudest, sadist, shrewdest, soundest, stupidest, weirdest, widest
Saddest sounds like:
sadist, sawdust, scotched, seduced, sketched, southeast, southgate, southside, southstate, southwest, staccato, stacked, staged, stake-out, staked, stakeout, stashed, stateside, stateswest, statist, steketee, sticht, stickiest, stitched, stocked, stockett, stoked, stuccoed, swatched, sweatsuit, sweetest, switched