Onex rhymes with:
necks, nex, aix, atx, beck's, becks, blech's, caltex, checks, cmx, convex, czechs, dec's, decks, dex, eckes, ex, execs, fedex, flecks, flex, govpx, heck's, hex, jex, lex, meckes, megaplex, mex, necks, nex, nobec's, peck's, perplex, plex, quebec's, rex, sex, sheck's, shek's, specks, specs, tech's, techs, teck's, tex, treks, triplex, vex, wall-tex, wrecks, x, x.
Onex sounds like:
oehmens, ohioans, ohm's, ohms, ohnemus, omaha's, omans, omega, omens, ominous, onassis, onassis', onassis's, once, one's, oneness, oneok, ones, ones', onex's, ong, onions, onishi, ons, onus, onyx, ounce, ounces, owen's, owens, owens's, owing, owings, owning, owns