bugaboo, bane, gripe, stumbling block, pet peeve, drawback, impediment, irritant, problem, achilles heel, preoccupation, peeve, annoyance, hindrance, conundrum, headache, concern, whinge, culprit, anathema, bogeyman, obstacle, bogyman, whipping boy, leitmotif, factor, differentiator, buzzword, thorn, shortcoming, hurdle, constraint, furphy, paradox, thing, euphemism, trump card, dilemma, determinant, imponderable, whinger, issue, occupational hazard, bogy, moaner, sine qua non, waster, bedfellow, saving grace, obsession, misconception, sticky wicket, red herring, reason, dogging, chunter, watchword, pitfall, qualm, niggle, shibboleth, nightmare, hinderance, irk, symptom, bete noire, blights, dampener, worry, upshot, aspect, determiner, luddite, characteristic, holy grail, mantra, hobbyhorse, tactic, motivator, hallmark, haunts, blindspot, enigma, detractor, downfalls, facet, priority, nub, trope, hackles, tetchiness, scourge, irritation, criterion, specter, element, consequence, spanner, nemesis, flashpoint, distinguishing characteristic, downsides, bogey, bugbears, grievance, carnival, curse, danger, evil, scapegoat, vice, favorite, favourite, marvel, nuisance, want, boast, burthen

monster

bogeyman, booger, boogeyman, bugaboo