Here's what rhymes with hellogoodbye.
by die buy tie bi bye dye pi pie thai dei goodbye ty tai my high why dry lie thy try y guy vi hi shy sigh chi fi hy nigh spy thigh vie ly ply psi quae rye wir awry hai lye mai muy nai pry tri trie wry cy fy kai lai luy mei pri sy thei wai phi sty stye apply cry fly sky deny defy fry sly belie pupae untie spry amebae turfy slier supply reply thereby imply nearby occupy rely whereby comply hereby alibi decry lullaby typify amoebae codify edify aquae bonsai deify retry triply stupefy lanai ripply banzais overbuy justify modify testify butterfly certify gratify notify underlie pacify ratify rectify standby beautify termini terrify descry liquefy overlie resupply acidify ossify blowfly petrify liquify scurfy barfly prettify shanghai beatify drachmai speechify syllabify dandify yuppify identify satisfy clarify multiply nuclei qualify specify alkali classify signify verify glorify purify quantify alveoli amplify fortify magnify nullify samurai unify solidify crucify dignify mollify mortify oversupply ramify vilify firefly mystify preoccupy stratify stultify ultrahigh vivify calcify horrify misapply reunify overfly scarify versify hyperbolae mummify vitrify gentrify refortify solemnify stimuli simplify diversify falsify objectify personify demystify detoxify dragonfly electrify emulsify reclassify revivify cumuli dissatisfy exemplify intensify indemnify declassify disqualify oversimplify misidentify transmogrify