頑な

かたくな

Adjectival nouns or quasi-adjectives (keiyodoshi)

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頑張ってがんばって

do your best; go for it; hang in there; keep at it

頑張ったで賞がんばったでしょう

try-hard award; consolation prize

頑張れがんばれ

hang in there; go for it; keep at it; do your best

頑張りがんばり

tenacity; endurance

頑張りやがんばりや

hard worker; person who perseveres; person who doesn't give up; eager beaver; bitter-ender