S/he’s definitely hyper-melanistic, presumably by chance/from wildtypes. I don’t know if Black Night/Black Pearl/Charcoal/Akoya/Carbon could be applied as those indicate specific bloodlines (or did at one point). Where did you get him/her, and how long have they been with you? Can you show us a pic of their vent/tail base? Then we can tell you gender.
If you are concerned about care and unsure if you’re doing the right thing, I suggest you look through the posts in the Gecko category on this forum, and read the ones tagged ‘leopard gecko.’ Then you’ll get a lot of info, and see the tips people have given previously, including husbandry reviews.
Geckos often get darker with age, sometimes a lot. Kind of the opposite grey horses, which turn white with age. In the case of your kiddo, she has turned out awesome! Geckos can also darken a bit when cold, but not to such a degree.
Though I disagree with @westridge , and I think she was in pretty typical shape for a pet shop juvie leo when she was little (yes, too skinny, but especially dehydrated), I agree that she appears to be in ideal body condition currently, and that’s the important thing.