Synonyms and related words :
Tartar, anomaly, bear, complainer, crab, crank, dragon, feist, fire-eater, freak, fury, grizzly bear, grouch, grouser, growler, grumbler, hothead, hotspur, individualist, inner-directed person, misfit, naysayer, nonconformist, oddball, sorehead, sourpuss, sport, ugly customer, zero hour