According to SOWPODS2, there are 543 words between 2 and 15 letters which end with the letter X:

2-letter words:

ax, ex, ox

3-letter words:

box, cox, dex, dux, fax, fix, fox, gox, hex, hox, kex, lax, lex, lox, lux, max, mix, mux, nix, nox, pax, pix, pox, pyx, rax, rex, sax, sex, six, sox, tax, tex, tix, tux, vex, vox, wax, wex, wox, yex, zax, zex

4-letter words:

apex, brux, calx, coax, crux, doux, eaux, faix, falx, faux, flax, flex, flix, flux, grex, hoax, ibex, ilex, jeux, jinx, jynx, lanx, lynx, minx, onyx, oryx, plex, prex, roux, ulex, yunx

5-letter words:

addax, admix, affix, annex, beaux, bemix, bolix, borax, calix, calyx, carex, choux, cimex, codex, comix, culex, cylix, desex, detox, dewax, embox, enfix, fedex, forex, galax, hapax, helix, hyrax, immix, index, infix, kylix, latex, limax, linux, lurex, malax, mirex, murex, panax, phlox, podex, pyrex, radix, redox, redux, refix, relax, remex, remix, retax, rewax, salix, silex, sorex, telex, unbox, unfix, unmix, unsex, untax, varix, vibex, vitex

6-letter words:

adieux, afflux, auspex, banjax, bembex, bembix, biflex, bijoux, bollix, bollox, bombax, bombyx, boyaux, carfax, carfox, caudex, cervix, chenix, climax, coccyx, commix, confix, convex, cortex, cowpox, deflex, dentex, diplex, dogfox, duplex, earwax, efflux, forfex, fornix, frutex, hallux, handax, hatbox, haybox, hotbox, icebox, imbrex, implex, influx, isolex, jawbox, larnax, larynx, lummox, magnox, mastix, matrix, meninx, muskox, nontax, orifex, outbox, outfox, pegbox, phenix, pickax, poleax, pollex, prefix, premix, pretax, prolix, reflex, reflux, scolex, silvex, skybox, smilax, spadix, sphinx, sphynx, storax, styrax, subfix, suffix, suplex, surtax, syntax, syrinx, teabox, tettix, thorax, tutrix, unisex, vernix, vertex, volvox, vortex

7-letter words:

abrasax, antefix, anthrax, antisex, antitax, apoplex, apteryx, aruspex, bandbox, bateaux, beatbox, beeswax, boombox, bostryx, broadax, bureaux, cadeaux, carapax, cashbox, celotex, chamoix, choenix, coalbox, coannex, complex, conflux, coteaux, deindex, distrix, editrix, equinox, farebox, feedbox, firebox, flummox, fowlpox, funplex, gateaux, gearbox, gravlax, hellbox, homosex, humidex, jambeux, jukebox, kickbox, kleenex, lockbox, mailbox, milieux, minimax, narthex, oratrix, outjinx, overlax, overmix, overtax, packwax, panchax, paradox, pemphix, perplex, perspex, phalanx, pharynx, phoenix, pillbox, postbox, postfix, posttax, princox, reaffix, reannex, rectrix, reindex, reseaux, salpinx, saltbox, sandbox, sealwax, seedbox, shoebox, showbox, simplex, soapbox, sonovox, spandex, talkbox, tectrix, telefax, teletex, toolbox, tortrix, treewax, triplex, tubifex, vaudoux, victrix, vitraux, woadwax, woodbox, woodwax, workbox

8-letter words:

aftertax, anthelix, appendix, aviatrix, bandeaux, batteaux, berceaux, biconvex, bobbysox, bordeaux, brainbox, breadbox, camaieux, carnifex, chapeaux, chateaux, cicatrix, cineplex, clackbox, clangbox, coturnix, couteaux, creatrix, crucifix, curatrix, curtalax, cybersex, disannex, earthwax, econobox, epicalyx, fabliaux, fourplex, genetrix, genitrix, giambeux, haruspex, heretrix, heritrix, homeobox, horsebox, horsepox, intermix, interrex, intersex, jambeaux, janitrix, loosebox, lunchbox, manteaux, matchbox, megaplex, microlux, millilux, mirepoix, morceaux, nouveaux, octuplex, opopanax, orthodox, paintbox, parallax, phorminx, plateaux, ponceaux, pontifex, precieux, quadplex, quincunx, rondeaux, rouleaux, sardonyx, saucebox, scrumpox, smallpox, snuffbox, soundbox, spinifex, subindex, superfix, supermax, supersex, supertax, sweatbox, swinepox, tableaux, toadflax, tonneaux, tractrix, transfix, trumeaux, undertax, videotex, watchbox, waterpox, zelatrix

9-letter words:

aboideaux, aboiteaux, antihelix, bisectrix, decomplex, dictatrix, directrix, disclimax, dorsiflex, earthflax, fellatrix, flambeaux, gogglebox, gravadlax, heterodox, homoeobox, letterbox, mediatrix, metroplex, multiplex, neocortex, pepperbox, piscatrix, pompholyx, prehallux, prepollex, priedieux, prothorax, rattlebox, religieux, retroflex, shadowbox, spondulix, strongbox, subclimax, subcortex, submatrix, superflux, testatrix, tinderbox, tuckerbox, unperplex

10-letter words:

anticlimax, bordereaux, chalumeaux, chatterbox, chickenpox, circumflex, coadjutrix, contraplex, dominatrix, gaspereaux, generatrix, googolplex, groundprox, inheritrix, initiatrix, mesothorax, metathorax, moderatrix, nectocalyx, noncomplex, oropharynx, prattlebox, precentrix, protectrix, quadratrix, quadruplex, separatrix, spectatrix, subbureaux, superhelix, thunderbox, trisectrix, trousseaux, unorthodox

11-letter words:

androsphinx, arbitratrix, chalcedonyx, consolatrix, fricandeaux, hydrothorax, hypopharynx, merveilleux, nasopharynx, negotiatrix, neoorthodox, nonorthodox, overcomplex, progenitrix, prolocutrix, proprietrix, prosecutrix, sceuophylax, speculatrix, thoroughwax

12-letter words:

conservatrix, heteroduplex, hypercomplex, plagioclimax, pneumothorax, portmanteaux

13-letter words:

archaeopteryx, cephalothorax, hieracosphinx, immunocomplex, improvisatrix, interlocutrix, primogenitrix, ultraorthodox

14-letter words:

administratrix