Tough

strong hard solid tough as nails durable firm robust vigorous resilient healthy conditioned fit hardened resistant brawny stout rugged hardy stalwart mighty tenacious unyielding inflexible rigid sinewy cohesive dense strapping seasoned steeled tight unbreakable fibrous flinty withstanding leathery lusty molded hard-bitten indigestible stiff

stubborn firm hard fixed severe harsh strict inflexible cruel violent adamant unyielding immovable intractable resolute uncompromising obdurate callous headstrong unbending terrible fierce desperate immutable unalterable unforgiving pugnacious vicious savage drastic hard-line hard-nosed hard-shelled hard-boiled hard-bitten ruffianly merciless unmanageable uncontrollable stiff taut narrow exacting confirmed ferocious refractory arbitrary

hard heavy demanding taxing severe trying exhausting burdensome onerous strenuous laborious troublesome exacting grievous intricate perplexing puzzling baffling knotty thorny stiff unyielding intractable resisting effortful toilsome labored uphill backbreaking weighty exigent irksome mean hairy handful no piece of cake wicked