Here's what rhymes with unfavourable.

Consider these alternatives

unfavorable / favorable favourable / favourabl favorable / unfavorable vagaries / bakeries fluctuations / relations undesirable / desirable unkind / kind unsympathetic / magnetic climatic / dramatic favouring / favoring owing / going unfavorably / favorably unfavourably / favourably vicissitudes / viscissitudes favourably / unfavourably uncomplimentary / century inferences / extensive weather / whether undesired / desired recessionary / very spite / might choppy / body