Don't know anything about Archenemy, but Fenris is really hard to pin down.
While he is God of Destruction, common sense understanding puts him below Destruction of the Endless. Note that there's nothing actually on panel that confirms that, but the Endless in DC embody their concept on an absolute level so in theory Destruction of the Endless should encompass Fenris as well.
He didn't make an appearance until God had already left creation and it had started crumbling. He fought a greatly weakened Lucifer and got his head blown off, but again we don't really have much of a reference point for what level Lucifer was at except that Lucifer was running more or less on empty at that point.
So where do we put him with no reference points and really no objective feats either? Half-assed cases could be made for anything between Skyfather level up to low abstract. Hell I could see some Vertigo-haters arguing even lower than Skyfather, and I wouldn't really be able to argue because of his relative lack of feats.
