Same word as ill-natured:

catty, churlish, crabbed, crabby, cross, crotchety, cussed, dirty, disagreeable, disobliging, dyspeptic, hot-tempered, ill-humored, irritable, malevolent, malicious, mean, nasty, ornery, perverse, petulant, spiteful, sulky, sullen, surly, temperamental, tempersome, touchy