艰巨
jiān jù · HSK 7
arduous
🏔️ 艰 hard + 巨 huge = a hugely hard task; jù echoes giant (巨 = giant)
巨 means giant or huge, so 艰巨 is a difficulty scaled up to giant size: not just hard but formidably, mountainously hard. The jù sound lines up with the English giant for an easy hook.