The poor dog was badly mutilated in the accident, losing one of its legs.

mutilated 是动词 mutilate 的过去分词形式，表示"使残缺不全、严重损伤"。mutilate 来自拉丁语 mutilare（切断、毁坏），常用来描述肢体或器官遭受严重损伤或残缺的情况。