Depends on what it is to like about them!
Laurentina is definitely my favorite character-wise in terms of story, personality, development etc. I love her character growth and how she's able to overcome everything that's happened to her and face her reality with confidence. Also a huge fan of her character design/personality--I think that making a shark character who is elegant and graceful and maybe a bit of a snob but also craves violence the way a shark would is such a powerful juxtaposition. The fact that shes polite enough to use "watakushi" to refer to herself and has a generally refined manner of speech but also curses the most out of all the hunters and isn't afraid to speak her mind is just so, so good. I admire the way she accepts herself and chooses to live her life to the fullest (as much as I also think this is just a front and she's scared shitless deep down and will only show that side of herself to Skadi) and she is a source of strength and inspiration for me.
As for og nunmode Specter, I like her a lot because of her appearance/design! She similarly has the "graceful shark who craves violence" thing going on, but I feel like her state of mind makes her so much more intimidating than her awakened self. What I really like is the whole nun thing, as I am drawn to Christian/Catholic imagery and aesthetics and am a huge nerd about Christianity's role in art history. As someone who did not grow up in a Christian household, I have always been fascinated by it and love learning about religion/the Bible/monasticism from a cultural/historic standpoint. And of course, as a lesbian, the idea of being a nun is so appealing to me. As a result, I actually ended up getting into Arknights because my now-gf showed Specter to me back in 2021 and I was like holy shit nobody told me there was a shark nun in Arknights?? In case it's not obvious already btw, I love all the Hunters because I am a huge lover of fish and the ocean and marine life. Specter being a combination of a sea creature and a nun made her an instant favorite for me.
Lastly, in regards to Skadi, she is the one I am most attracted to. I do find her storyline compelling, and I think her journey of self-discovery is super cool especially when you put Ishar'mla in the mix, but I seriously wish they'd stop using her to pander to Docshippers. Regardless, the fact that she cares so deeply about Specter throughout the story and fights for her and protects her and never gives up on her is extremely touching to me. As someone who has had my own struggles with mental illness, I adore the idea of someone caring for me and devoting themselves to me like that. (And I am lucky to have someone who does! <3) Also I just think she's really hot. Her og E1 design is my favorite, but I really do love her portrayal as a fearsome god in IS3 so that design has also become one of my favorites. But I really do like the rugged mysterious hunter look the most... Her voice is so mellow and soothing, and she seems scary but she's so sweet... She is the ideal woman, a guard dog who will protect me but is on my leash and is so devoted to me that she will obey my every command. Strong on the outside and a little pathetic on the inside. And it's so cute that she likes pizza :)