Below are a few suggestions for making an unrealistic character become a real character that people will either fall completely in love with, or will simply hate.
Either way, the character - antagonist or protagonist - will draw your reader into your book, if you develop them right.
Don't make your characters boring. Give them some type of tic, action, flaw, or surprise that separates them from any other character your reader has connected with. For example, look at the characters of The Goonies. It is one of my all time favorites. Not for the story line but for the characters involved in the adventure. I fell in love with each character years ago, and they still linger in my mind. Make each character memorable in one way or another. Chunk? Sloth? Mikey? Data? Each of them I can remember perfectly.
A perfect character should have flaws. Not a single one of us are perfect, and your characters should not be either. They are boring. They are unlovable. They are unrealistic. Your reader will not relate to them. And worst of all, if they can't 'feel' that they know that character, they will back out of your story. A reader MUST connect in some way with your characters.
First thing's first. Decide what archetype each character will be. Here are a few character types to choose from. a) The Leader - Mikey b) The Hunk - Brand c) The Funny One - Data d) The Trickster - Mouth e) The Smart One - Stef f) The Bully - Mama Fratelli g) The Mentor - I see Sloth here! h) The Loner Chunk; although he is always trying to fit in i) The Cheerleader Type - Andy Well, you get the gist, right? Use your imagination!
Each character should have a past. They should have hair color, eye color, a history of where they came from and what made them who they are. Here is a small list of things to think about when developing characters a reader can relate to. But it's not everything. I have some downloadable worksheets to help you at this link. https://lisasimpsonbooks.com/all-about-characters
1.) Backgrounds - Where do they come from? Who are their parents? Heritage? Why do they feel the way they do? Was their childhood stricken by poverty or were they born with a silver spoon?
2.) Do they have a bad habit or nervous tic? Nail biting? Chewing the inside of their cheek or their lip until it bleeds? Playing with their hair? Always combing their hair? Digging their nails into their palm? Do they not shower enough? What do they do when they become stressed about something?
3.) Strengths or weaknesses? What is their strongest asset? What is the link that make them the weakest? Do they put their foot in their mouth? Can they talk their way out of a bad situation? Can they run faster than a speeding bullet? Does their hair make them strong? What are they good at? What are they bad at? What are they afraid of?
4.) Motivation - What is their purpose in your story? What makes that character keep your plot going or moving forward? Why do they do what they do? If their motives don't make sense in the story, they won't make sense to your reader.
5.) Features of your character - what makes them stand out? Chunk loved to eat and was fairly chubby. (to say it nicely) Data loved to invent things but they never quite worked the way he wanted them to. Mikey had braces even though when Andy kissed him in the dark, she thought Brand had suddenly gotten braces. Steph had glasses and couldn't see without them. Mouth was just...Mouth
6.) Give each of your characters their own voice. Do they have a slang word they say a lot? Do they have an accent? If they do, make sure you spell it and write it that way. Are they always loud? Do they talk softly? Do they always use the wrong words when talking?
7.) Make sure your characters are different. Don't make them all have black hair. Don't make them all talk the same. Give some of them a different skin color, hair type.
These are just some of the suggestions I have for you. I keep an ongoing spreadsheet in Excel filled with ideas of characters. My simple spreadsheet is downloadable on the link above. Every time I think of something to add to a character, I open my spreadsheet, and either add that idea to a current character, or I start a new one. It might surprise you that when you create many different characters on a spreadsheet, you just might look at them, piece them together, and come up with a whole new story!