Here's what rhymes with unnecessary.
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belly allele jelly smelly deli telly underbelly vermicelli heavy fairly semi heady faery sedgy veggie many ready healthy rarely steady barely petty levy penny fleshy levee messy sentry sexy sketchy sweaty unfairly vestry hefty jetty machete teddy bevy jenny thready kepi leggy recce especially assembly scarcely wealthy deadly lengthy freshly gentry unhealthy frenzy squarely antennae carefree medley spaghetti unsteady belfry deathly fleshly gayety halfpenny stealthy sullenly confetti fidgety hostelry pebbly tempi testy breathy dressy pesky effendi lefty wetly already twenty friendly elementary gently plenty epilepsy densely deftly coquetry tensely trendy aplenty libretti marquetry adeptly directly correctly expressly immensely unfriendly excellency sacredly ambivalently baronetcy deviancy maidenly reassembly ineptly preciously woodenly intensely intently apoplexy confusedly narcolepsy indirectly complementary incorrectly equivalently grotesquely complexly catalepsy circumspectly cognoscenti penitently