ご苦労様[gokurousama] thank you very much for your ...
御苦労さん[gokurousan] I appreciate your efforts
苦力[kuurii] coolie
悪戦苦闘[akusenkutou] hard fighting
気苦労[kigurou] worry

夜露死苦[yoroshiku] well
狭苦しい[semakurushii] cramped
勤苦[kinku] toil and hardship
苦い[nigai] bitter
苦しい[kurushii] painful

踠く[mogaku] to struggle
踠き[mogaki] struggle

踠き苦しむ[mogakikurushimu] to writhe in agony