きつい (translations)→ arduous baleful bitter broad corrosive demanding explicit fierce good grave hard nasty painful palpable sharp sharply sharpness shattering steep strong tightly tough
しつこい (translations)→ heavy perpetual stubbornly such tiresome unwanted
しぶとい (translations)→ formidable greedy resistant tireless
頑固 (translations)→ indomitable resolute
頑固な (translations)→ dogged flinty headstrong intransigent mulish opinionated willful
頑固に (translations)→ doggedly firmly
執念深さ (translations)→ doggedness implacability
執拗に (translations)→ consistently determined dog-like endlessly insistent obstinately persistent relentlessly steadily tenaciously
