Must've rhymes with:
congestive, digestive, esteve, exhaustive, festive, restive, suggestive, abortive, accommodative, accumulative, accusative, acquisitive, active, adaptive, addictive, additive, adjective, administrative, adoptive, affective, affirmative, airmotive, alliterative, alternative, anti-infective, anticompetitive, appointive, appreciative, argumentative, assaultive, assertive, attentive, attractive, authoritative, automotive, captive, causative, co-operative, cognitive, collaborative, collective, combative, commemorative, communicative, comparative, competitive, conductive, congestive, connective, consecutive, conservative, constructive, consultative, contemplative, contraceptive, convective, cooperative, corrective, corruptive, counterproductive, creative, cumulative, curative, deceptive, decorative, defective, definitive, degenerative, deliberative, demonstrative, derivative, descriptive, destructive, detective, digestive, dilutive, diminutive, directive, discriminative, disincentive, dispositive, disruptive, dissipative, distinctive, distributive, duplicative, effective, elective, elucidative, emotive, emptive, eruptive, esteve, evocative, executive, exhaustive, expletive, exploitative, exploitive, facultative, federative, festive, figurative, fixative, formative, fugitive, furtive, generative, hyperactive, hypersensitive, illustrative, imaginative, imitative, imperative, inactive, inattentive, incentive, indicative, ineffective, infective, infinitive, informative, initiative, injunctive, innovative, inoperative, inquisitive, insensitive, instinctive, instructive, interactive, interpretive, introspective, intuitive, invective, inventive, investigative, irrespective, iterative, laxative, legislative, locomotive, lucrative, manipulative, meditative, motive, narrative, native, negative, neoconservative, nonautomotive, noncompetitive, noncumulative, nonexecutive, nonnative, nonproductive, normative, nutritive, objective, obstructive, octave, operative, overactive, oversensitive, palliative, participative, pejorative, perceptive, performative, perspective, photoconductive, photorefractive, plaintive, positive, predictive, preemptive, prerogative, preservative, presumptive, preventative, preventive, primitive, proactive, probative, productive, prognosticative, prohibitive, projective, prospective, protective, provocative, punitive, putative, qualitative, quantitative, radioactive, reactive, receptive, reconstructive, recuperative, redemptive, redistributive, reflective, refractive, regulative, rehabilitative, relative, remunerative, rep., repetitive, representative, reproductive, respective, restive, restorative, restrictive, retroactive, retrospective, secretive, sedative, seductive, selective, sensitive, speculative, stimulative, subjective, substantive, suggestive, superconductive, superlative, supportive, talkative, tentative, ultraconservative, unattractive, uncompetitive, uncooperative, unimaginative, uninformative, unproductive, unreceptive, unrepresentative, vegetative, vindictive, vituperative
Must've sounds like:
macduff, mastif, mastiff, mcduff, mcduffee, mcduffie, mcduffy, might've, misstep, mustafa, mystify