tough

feeling physical discomfort or pain (`tough' is occasionally used colloquially for `bad')

substantially made or constructed

making great mental demands

very difficult

unfortunate or hard to bear

resistant to cutting or chewing

physically toughened

not given to gentleness or sentimentality

violent and lawless

a cruel and brutal fellow

an aggressive and violent young criminal

someone who learned to fight in the streets rather than being formally trained in the sport of boxing