Unpack rhymes with:
pac, pack, pak, paque, repack, spack, spak, aback, ack, adak, akc, attack, back, backe, bak, bakke, beaulac, black, brac, brack, brakke, braque, cac, caq, chirac, clack, crack, dac, dack, dak, dulac, fac, flack, flak, hack, hacke, haq, haque, jac, jack, knack, knick-knack, krack, kracke, kwak, lac, lack, lak, mac, mack, macke, mak, nack, nacke, pac, pack, pak, paque, plack, placke, plaque, post-attack, ptak, quack, rack, rak, repack, sac, sack, sak, schack, schlack, schnack, schrack, shack, shaq, slack, smack, snack, spack, spak, stac, stack, strack, stracke, tac, tack, tacke, tak, trac, track, trak, vanvlack, wack, whack, wrack, yack, yak, zach, zack, zak
Unpack sounds like:
umbach, umbaugh, unambiguous, unbook, univisa