perseverative

hard-nosed indefatigable relentless resolute single-minded staunch steadfast stubborn tenacious unflagging unshakable unyielding

firm obstinate persevering steady unbending

adamant bullheaded hanging tough hardheaded inexorable inflexible insistent mulish obdurate perseverant pertinacious pigheaded rigid

irresolute surrendering unreliable weak yielding

flexible soft unstable

indifferent undetermined