ticklish

hypersensitive, oversensitive, sensitive, supersensitive, tender

choleric, crabby, cranky, cross, cross-grained, crotchety, grouchy, grumpy, irascible, irritable, peevish, perverse, pettish, petulant, prickly, quick-tempered, raspy, ratty, short-tempered, snappish, snappy, snarky, snippety, snippy, stroppy [British], stuffy, testy, waspish

bearish, bilious, cantankerous, curmudgeonly, disagreeable, dyspeptic, ill-humored, ill-natured, ill-tempered, ornery, querulous, surly

abstract, abstruse, complex, complicated, hard, intricate, involved, recondite, serious

problem, scabrous, stubborn, troublesome, troublous, vexatious, vexing, worrisome

burdensome, demanding, discommoding, exacting, exhausting, importunate, inconvenient, onerous, oppressive, painful, stressful