At this point we are treading in a bit of unknown territory. MC had too much trouble versus the Twins. Yes Devana can't really do much to him, but Evander can and a level 2 shouldn't have such an easy time going against a level 3.
I have talked about how this scene leaves me with a very bad aftertaste. A murderous (as stated) MC should have already killed Devana with a stray tail and slapped Evander with half the forest by the end, but instead he was on the defensive till Shen got bored and decided to end it without any hint at resistance on MC's part.
So while I think that the Moon twins are beneath him, they will end up being the next roadblock, especially if they evolve. After all, there exist indications that they tend to grow much faster than other Superhumans. Of course MC also has an exceptional growth so we can't yet tell how they compare,
On the other hand, it doesn't feel like the Moon twins are supposed to be Antagonists, at least not by default.
These are my most anticipated scenarios:
1) A huge MC + Foxglove Twins vs Shen + Moon Twins fight.
I really like the Foxglove sisters and I want them to take a more active role. One of the problems however is that time doesn't wait for anyone and a brand new level 1 can't really compete without some form of timelapse. The idea that Twins somehow grow faster than usual however, could be the key to let them be relevant.
Such a fight that ends up in MC's favor will be huge. It will show that MC is superior as both a Superhuman and as a trainer, and set the Foxglove twins as useful allies rather than some newbies who still need to find their footing.
2) Foxglove Twins getting merged into a Superbeing, permanent or not.
The Fusion scenario was one of the first wild theories since we got confirmation that this is the "Twins Arc". It's also a cool way to avoid the time problem. It will be a new and exciting variable, with the potential to be formidable without going through the usual steps.
The Foxgove twins are shown as being the exact opposite. One is haphazard and extremely talented, the other is extremely dilligent but an underachiever in comparison. One is cold the other is hot etc.
And I think that this is why the fusion theory is so exciting. Because they have the potential to complete each other.
3) Solo MC vs multiple Ella kids.
This will require some setup, but MC should have started getting frustrated at this point. While his personal growth is well on it's tracks, he has very limited control over what is happening around him.
So at this point I think that a "Jean-Claude Van'Damme getting angry and owning shit" moment will work wonders to set the tone for the things to come. MC is supposed to become the best but his victories are always by the skin of his teeth and he didn't really have a chance to showcase "dominance" up to this point.