Alright, I'll give it a shot (I'll try to be gentle but idk where the line is drawn whoOps)
Buck-
Overview
Pretty good here! Nothing too vague or anything.
Looks
Oof, pretty risky to put the words "i don't know" when creating a character. (He's your character, you could give him everything you need to know about him down to the blood type!) I noticed you didn't have his height either, but that can factor in to his weight! The average weight for a 17 year old should be around 130-150 lbs., but it also depends on his height. The description of his hair, eyes, and skin are good, but a little general. There are other shades of white, (pale, olive, tan,) ya know? And it might also help to identify where the scars and freckles are. (And what kind of scars)
Nature
The nature tab is good, but I think it needs a bit more structure. While this is exceptional, it only gives a general idea of who he is, also, you might need to add a few more flaws, but make sure they don't contradict any other aspects about him! (for instance, it says he has a talent for planning, but one of his flaws is acting before he thinks. maybe change one of the two). Loving the character so far!
Social
If he doesn't have a religion, he'd be agnostic (or Atheist) and if you want to get really in depth, explain why he's not religious. was he never introduced to a religion? is he just not interested? another good tip; with all of the favorites, ask yourself "why is this his favorite?" and then add the answer. it helps give depth to the character.
History
Wow, this is quite a story. I might make a few comments that'll be answered in later characters, but oh well. first of all, who (or what) is Ravenna? How is she capable of taking down so many villages with armies? How well are they trained, and how unstoppable is Ravenna? surely she must have a weakness, else she could enter the territory of a Mary Sue. How does Leilson pertain to the story? Who is he to Buck? What is Leilson's story? to take it further, what is Ravenna's story? what is Edric's story? All of these things could add another dimension to your story.
Magic
Good extra tab to explain his magical powers, but it might help to specify what types of elemental magic he's capable of. Can he bend water, earth, fire, and air? can he manifest these things? how short of a length of time has he known about it? does he plan on practicing at all, despite being prejudice against it?
Overall, I really like this character. He sounds like a very lovable guy and I'm excited to see where he goes! The most general tip I often use on myself when creating a character (or even developing one) is to ask the question, "Why?"
I'll try to do the other characters next, but it might take me a bit, sorry haha.