彼(かれ)等(ら) kareraは wa楽(らく) rakuに ni任(にん)務(む) ninmuを o成(な)し()遂(と)げ()た() nashitogeta。 They accomplished the task with ease. Literal They [topic-は] easily task [object-を] accomplished. 楽に means 'easily, with ease.' 任務を成し遂げた means 'accomplished the mission/task' — 成し遂げる is a formal compound verb. workcompound verb
彼(かれ)等(ら) kareraは wa楽(らく) rakuに ni任(にん)務(む) ninmuを o成(な)し()遂(と)げ()た() nashitogeta。 They accomplished the task with ease. Literal They [topic-は] easily task [object-を] accomplished. 楽に means 'easily, with ease.' 任務を成し遂げた means 'accomplished the mission/task' — 成し遂げる is a formal compound verb. workcompound verb