'Adversaries' in the Bible

because a wide door for effective service has opened to me [in Ephesus, a very promising opportunity], and there are many adversaries.

And in no way be alarmed or intimidated [in anything] by your opponents, for such [constancy and fearlessness on your part] is a [clear] sign [a proof and a seal] for them of [their impending] destruction, but [a clear sign] for you of deliverance and salvation, and that too, from God.