stubborn; obstinate

tenacious; hard to defeat

naughty

urchin

stubborn and obstreperous; naughty and mischievous

gangster; bandit

obstinate; stubborn; pig-headed

unruly people; rebellious subjects; disloyal citizens

stubborn illness; chronic disease; (fig.) deep-seated problem; systemic issue

see 頑疾|顽疾[wan2 ji2]

blunt (instrument); stupid; thick-headed