the act of somebody/something being completely destroyed 灭: 某人/某物的行为被完全摧毁the annihilation of the whole human race 全人类的毁灭
the complete defeat of somebody/something 歼灭: 某人/某物的彻底失败The Brazilian needed just 82 minutes to complete the annihilation of his opponent. 巴西人只需要82分钟就完成了对对手的歼灭。