Anyone who has managed the feat of getting with both sisters (Anna & Rebs) and still keep all relationships intact, should be No. 1 on your Bad@$$ Hero
list and Dastardly Villain
list at the same time. Give the man his props, just saying.
Unfortunately for Carl, his destiny is to have an ignominious end. Because if Anna doesn't get him, the major crime syndicate, that Sergey's gang has now been shown to be a small part of, almost certainly will. And those guys look pretty scary. Not the kind of people you want to steal money from, and then get found out. And Carl didn't just betray Anna and Rebecca, he was planning to kill them, once they'd outlived their usefulness. So I foresee a very bad ending for him. But at least he'll be going out with a bang instead of a whimper.
The more I think about it, I think cuck Carl was obviously just a cover. He was quite happy to share Rebecca, because he was never remotely interested in her, beyond someone to keep his bed warm. The Rebecca kidnapping was a pretext to draw Sergey into an ambush. Because the bullet that Andrew unexpectedly intercepted, was intended for Sergey (in the text it says Fitzgerald's henchman was aiming for Sergey when he fired). And if Andrew hadn't done that (because he was worried Anna would get killed) then Sergey would probably have died in that shootout. And my guess is, that Anna, Rebecca, Andrew and Michael would then have followed him, shortly afterwards, leaving Carl as the unopposed leader of Sergey's drug operation.
So unbelievably perhaps, it could be that Andrew, of all people, was (totally unintentionally) responsible for thwarting Carl's masterplan?