malcontent

noun

the trouble was caused by a group of malcontents:

troublemaker, mischief-maker, agitator, dissentient, dissident, rebel, disruptor;

discontent, complainer, grumbler, moaner, fault-finder, carper;

informal stirrer, grouch, grouser, griper, nitpicker, bellyacher, beefer;

British, informal whinger;

North American, informal kvetch.

adjective

a malcontent employee:

disaffected, discontented, dissatisfied, disgruntled;

fed up, restive, unhappy, annoyed, irritated, displeased, vexed, peeved, piqued, put out, malcontented, resentful;

rebellious, dissentious, factious, troublemaking, grumbling, complaining, fault-finding, carping;

informal nitpicking, bellyaching;

British, informal browned off, cheesed off, brassed off, not best pleased;

North American, informal hacked off, teed off, ticked off;

vulgar slang pissed off, peed off.

▷antonyms happy.

malcontent Oxford Dictionary of English