When you are writing a story with characters, you need to focus on their development. If they aren’t developed properly, you might have readers not even finishing your book. Your readers have to be able to connect with your characters.
Connect vs. Like
I’m not saying you have to like every character. In fact, you don’t want that. Liking every character would ruin so many stories. Seriously! Who wants to like Hannibal Lector? Nobody. But you need to connect to him. He have to be able to feel the emotions emanating from him.
Liking a character means you cheer for them and want them to win. If you want to cheer for Lector, I might be a tad bit concerned. But you need to connect to him. You need to react to him. You need to revile him yet possibly be intrigued. Again, I would worry if you liked him.
Connect means you react to their actions. You pull when they push. You cry when they hurt or hurt someone. The emotions reach out to you.
Cannot be Flat
In order to connect to a character, they have to have depth. They cannot be flat. Every person has unique characteristics. They have quirks. They have unique traits. They have depth. They cannot be flat.
Flat characters are boring. Readers might even not finish a book with flat characters. You have to give them life. That is what helps the reader connect to them. Even the dark evil ones need to have depth to them. They need to be seen as real beings which means they have a past and emotions. Readers latch on to these.
Think of which characters you really connected with. What was it about them that allowed that to happen? What made a character interesting to you even if you didn’t like them?