きつい の訳語→ 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 の訳語→ heavy perpetual stubbornly such tiresome unwanted
しぶとい の訳語→ formidable greedy resistant tireless
頑固 の訳語→ indomitable resolute
頑固な の訳語→ dogged flinty headstrong intransigent mulish opinionated willful
執念深さ の訳語→ doggedness implacability
執拗に の訳語→ consistently determined dog-like endlessly insistent obstinately persistent relentlessly steadily tenaciously