arduous baleful bitter broad corrosive demanding explicit fierce good grave hard nasty painful palpable sharply sharpness sharp shattering steep strong tightly tough
heavy importunate perpetual stubbornly such tiresome unwanted
formidable greedy resistant tireless
dogged flinty headstrong intransigent mulish opinionated unpliable willful
doggedness implacability inveteracy
consistently determined dog-like endlessly insistent obstinately persistent relentlessly steadily tenaciously