I admit that you have given me some good things to think about. These are two different groups, one knowing, the other ignorant. It is apparent that two classes are represented since the article is repeated in the original.
Vengeance is from ekdikesis, that which is enacted out of justice.
It does not imply a spirit of revenge. In the sense here mentioned, one may know God and never even have heard of the gospel. Man can be under no governing principle of which he has never heard, and to which he has no personal access. He cannot make a choice if he does not know there is an alternative. He cannot decide to be under the Lordship of Jesus if he has never heard of Jesus.