Efsun's story is actually really interesting to me because it deals with an aspect of this mafia life that I always felt they were approaching but dancing around with the Koçovali and Kurtulus families as well as the Erdenets. And that's seeing your enemies as people.
We as an audience (for better or worse depending on each of us) have been allowed to see the enemies' complex human lives and relationships. But the Koçovalis never quite get there. (Sure there are enemies they don't kill for various reasons but not generally because of empathy)
Efsun started as someone who just wanted to avenge her father by killing his murderer. Which is like, a very reasonable instinct in this world. And now she finds herself in the impossible position of having to reckon with the fallout of what once felt like a righteous action.
She has had to come to terms with the fact whether it was justified or not, her actions irrevocably wounded an entire family and community of real living breathing people. Not just Yamaç. She's being forced to see them all. To grapple with her decisions on a broader scale.
One thing I've always loved about this show is that they make sure we see every person as human, even if just for a moment. We aren't just blindly rooting for bad guys to be mowed down like a video game. We see the broader reaching destruction brought by each death.
All this is just to say I like that they told this story, whether you like her or hate her or whatever, it's an interesting exploration of what this lifestyle they are so invested in really *means*.