In debate, he was a formidable opponent.

在辩论中，他是一个难以应付的对手。

With temperatures plummeting again to well below freezing, Muskoxen face the most formidable opponent of all, the Arctic winter.

气温再度骤然降下，远远低于零度。麝牛毅然面对最强大的对手，北极寒冬。