On the other hand they could be a bunch of dicks who just ran out of more primitive locals to kill and oppress....
It’s an intriguing mental exercise to think about such things, but in the end we have to fall back on those good old spiritual principles, yes the ones in the bible that talks about a God who created the universe for His pleasure.
If it weren’t for grace, nothing would happen at all. This is even apart from the question of sin, and what would righteousness and sinning look like with respect to an alien race if it existed.
Ultimately my faith remains that God is competent. If He has cameos of hostile alien races in the end times, our Christ is the same as the Christ that rules the universe and won’t have any trouble dealing with them.