Her sinister smirk in that final scene looks pretty similar to the one Kirigan would use, mirroring her nemesis once again. Alina may not be quite on par with Kirigan yet, but she is heading in the same direction, slowly transforming into the Darkling herself.
The fate of Alina's powers in the show and in the books
It's not been explained yet, of course, but it's safe to assume that the price Alina had to pay for using merzost to bring Mal back was having her “original” Sun Summoner powers corrupted and turning into a Shadow Summoner, like the Darkling used to be.
The newly-created Sun Summoners destroy the Fold and also partially return Nikolai to his former self. Tolya and Tamar Kir-Bataar manage to save Mal. However, Alina has lost her power.
While she doesn't lose her powers as a punishment, she isn't in the clear either. Instead, her consequences are darker – literally. In the final scene, Alina uses her powers again and finds them changed. To Alina's surprise, she performs the Cut with shadows like the Darkling rather than her former light.
TL:DR: The dynamic between the Darkling and Alina is far more complicated and nuanced than 'evil man manipulates vulnerable girl'. Did he have true feelings for Alina? Yes.
Basically, Kirigan is very lonely as an immortal being, so he's very invested in the idea that he and Alina belong together. She's been in love with her best friend, Malyen “Mal” Oretsev (Archie Renaux), since they were kids together in the orphanage of a small village called Keramzin.
Rather than raping or assaulting women, the Darkling tricks Alina into falling in love with him, his goal being to take Alina's power for himself and effectively enslave her.
Alina is automatically powerful just by being the Sun Summor. She destroyed the Fold, which was with the help of three amplifiers. Because of those amplifiers, she is in third place. Coming in at number two, we have the Darkling.
Alina would have had to go through some sort of head transplant to choose to be with that man. Instead, Alina chose Nikolai. She knew that Ravka needed stability and surety, and that was something a union between Nikolai and Alina would be able to offer. Shadow and Bone season 2 is now streaming on Netflix.
Better known as the Sun Summoner, Alina is the protagonist of the series. As one of the most powerful Grisha, she is the only one capable of saving Ravka from the Fold.
Although the book versions of Mal and Alina technically get a happy ending after the events of Ruin and Rising, it seems as though their television counterparts are going to have to wait a little longer to be together forever.
In the book, however, Alina uses merzost through her still-active connection to the Darkling in order to create her own nichevo'ya (shadow monsters like the Darkling uses) to fight back against him at the end of the second novel. As a result of her using the power that one time her hair turns permanently white.
This aspect has its roots in the books, but with very different circumstances. Between the novels Siege and Storm and Ruin and Rising, on which season 2 is largely based, Alina loses her Sun Summoner powers completely for a time after a fight with Kirigan.
Ulla is a half-sildroher songcaster and the half-sister of The Darkling via their late mother, Baghra. She is also known as Sankta Ursula of the Waves.
The Shadow Fold was created roughly 400 years prior to the events of the series and the Darkling was already an adult by then. An estimate would put him at 500 years of age, if not a bit older.
While searching for the last amplifier, Mal and Alina find out the truth about Mal's heritage. He is descended from Baghra's sister, making him a great-nephew of the Darkling. It also makes him an amplifier. He accepts this fate, understanding and willing to die for Alina.
Mal was oblivious to Alina's love from before book one even began. He slept with Zoya and countless others before he realised who was waiting by his back door.
In Leigh Bardugo's novel, Kirigan (Ben Barnes) stuns Alina (Jessie Mei Li) with an unexpected first kiss. Later, after they demonstrate Alina's abilities to the king's court, the two passionately make out and the narrative suggests they come very close to having sex before they're interrupted.
In the books, Alina and Mal end up getting their happily ever after, but it's not without complications. After Alina successfully kills the Darkling (nearly sacrificing Mal in the process, like in the show), most of Ravka thinks they're dead. They change their names, get married, and essentially go into hiding.
He has always wanted her light to balance his shadow. Their connection persists because of what The Darkling believes Alina to be. He is constantly referring to her as "my Alina," which is creepy, but that is the true depths of their connection.
As a human amplifier, the Darkling can even amplify Alina's Sun Summoning powers. As of now, these abilities and extensive history make him the most powerful Grisha and the most powerful character in Shadow and Bone.
Shadow and Bone
It is revealed that Alina had been subconsciously suppressing her power when she was tested as a child in Keramzin for signs of Grisha ability. It was as though she knew that if she was found to be a Grisha, she would be taken away from her best friend, Mal.
3 Alina and Darkling's Kiss
Alina makes the first move to kiss the Darkling (played by Ben Barnes) in the show, but this is not exactly what happens in the books; instead, he catches her off-guard and kisses her first.
(Note, Alina doesn't have her scar removed by Genya in the book, unlike the show, wanting to keep the memory of cutting her hand when she first realised she was in love with Mal.)