To paraphrase another famous bounty hunter; she's no good to him dead.
I'm beginning to wonder if even you know what Nack's up to.
So Nack's goal here is... what? I don't even know anymore. What's he trying to accomplish by betraying everyone so many times that, by now, anyone with an ounce of sense should murder him on sight? I can only assume he's somehow figured out how to become GOD, because any less power is going to get his head separated from his shoulders as soon as he makes that one little mistake the villains always make in these comics...
What Nack's trying to accomplish is getting off this mudball and making profit in the progress. Like he said way early, "Friends nothing, they're my paycheck and ride home."
Nack has also just proven that he's the smartest of the bunch. True Samus is a tactition but she'd of tried to kill her and absorb her... trying to do so before joining with Larvos.
Nack on the otherhand; it seems like he was planning for things to be like this the entire time. Have all the X's distracted with the Pirates and focusing on that defense because Samus, the only real fatal threat to them was there.
I'm going to have to agree with Waddledee there, I doubt Samus will even give Nack a ride home at this point. I'd just stuff him in a sack, shoot it a few times, smash it with a club, and chuck it in a ditch full of used needles and rabid ferrets.
I also agree with Waddledee. It seems that Nack has somehow become Omniscient, as there is no way he could have known to use a tranquilizer when a power beam could have sufficed (except if his power suit gives him the ability to read minds, and even that's a stretch).
Or he and Samus talked about the X parasites earlier...