Retarded rhymes with:
bombarded, discarded, disregarded, larded, unguarded, accorded, bombarded, discarded, disregarded, hoarded, larded, prerecorded, rewarded, safeguarded, unguarded, unrecorded, warded
Retarded sounds like:
rathert, rehydrate, reiterate, reiterated, retard, retired, retort, retorted, retread, retreat, retreated, retried, rodarte, rotert, rothert, rudyard