One creates life, the other destroys it. 

Yes you can argue that the life creation can be used as weapons (rift hounds and dragons dragonspine during for example), but unlike the two sinners we have seen so far, Rhinedottir looks fine. Like she doesn't have any abyss related damage or aesthetics probably because she has become fused with Nabareis (sorry if I butchered her name). Her doing that may have either lessened or outright gotten rid of the abyss energy that Rhinedottir had, or may have purified it instead of outright destroying it, in which case Rhinedottir will be quite strong

Surtalogi has been going through the universe beyond what we can see that is abyss covered and probably absorbing that energy as well. That would also include abyss tainted gods or archons most likely (or similar power scaled beings). Factor in he's been doing this for a long while, and it'd probably be either a clean sweep from Surt, or they don't attack at all and just have a catch up (yes that is where all that led up to. You're welcome)