1. Give them something to fear.

Everyone is afraid of something. Even if stoic characters claim to have no fear, it always exists and can change a person's behavior when they are forced to face them. For example, when Lexa's power was threatened by Roan, she acted on a whim and killed Queen Nia. Whatever fear(s) you give your characters should change their behavior and be somewhat of a drive for them. A common fear is one's loved ones dying, which is a staple to almost everyone.

2. Give them some enemies.

If your character has nobody opposing them, what's the point of the story? There should be one or more people in the story that your characters do not like and the feeling goes deeper than mutual dislike. Even if it's just the Grounders if your character is a Sky Person, giving your character enemies makes them much more concrete.

3. Remember that not everyone should like your character.

As much as we would like to, we can't make everyone like us. There is always going to be someone who doesn't like another person for whatever reason, so the same should be true for your character. Maybe someone hates their constant optimism because it seems unrealistic. Maybe someone dislikes what the character stands for or how they treat others. Clashing personalities is also a common reason for a mutual disliking. This is separated from the "enemies" tab because someone not liking your character doesn't have to make them sworn enemies. 

4. Give them a health complication.

What happened to all the anemics?? All the asthmatics??? All the diabetics?? Natural selection?? There are almost no health complications in the show except for the genetic disease in the McIntyre family that was never named or described in 5x13. I can't tell you how many people I know with asthma (including myself) and I know at least five people with diabetes. The fact that these people are nonexistent is pretty difficult to believe.

5. Give them allergies.

Since the Sky People have been in space for 97 years, they have never been exposed to real oxygen or pollen. Pollen can bring on those good ol' seasonal allergies– the runny noses, red and itchy eyes, sneezes, and scratchy throats. Even a Grounder character can have them because your body falsely detects pollen as dangerous. In your body's attempt to fight off what it believes to be harmful, it produces a chemical called histamine, which produces allergy-like symptoms. 

They can also be allergic to certain foods. Maybe they're a delinquent who is allergic to nuts, but they don't know it until 1x08 and they have a reaction. Maybe they're a Grounder from Floukru who's ironically allergic to fish. Some ideas are nuts, fish, shellfish, wheat, and various types of fruit.  

6. Give them a disability.

Disabled people freaking exist! They are very underrepresented in modern media. Whether this is a physical or mental disability, including it in your story can mean a lot for many people. Right now, Raven is the only disabled person on the show. I find it difficult to believe that not one person with Down Syndrome was born on the Ark recently; the life expectancy is currently at 60. That far in the future, I'd expect it to be higher. 

7. Remember that their family should be important.

Many authors, regardless of fandom, completely ignore the OC's parents and leave them almost completely out of the picture. Even if both of their parents are deceased, this should be an important factor in their life, like it was for Charlotte. For example, Murphy's father was floated for stealing medicine for him, causing him to set fire to the guard's living quarters. This is also the reason for his antagonistic attitude in season 1. Parental relationships were very important on the show; Sergeant Miller and Miller were one of my favorite dynamics. 

Our parents shape us into who we are. Their parenting choices & styles help make us who we are, good or bad. Pretending they don't exist or not mentioning them at all will make your character seem flat. 

8. Strengthen their backstory.

"Hi my name is Flinstone Quebec and I was a thief on the Ark." Okay. Is that all?

What is your character's backstory? What was their childhood like? Did they grow up poor, middle-class, or Privileged? Did they live with lots of friends in Flokru or were they forced to become a warrior at a young age in Azgeda? All of these points will segue us into the next one...

9. Recall that every personality trait must be there for a reason.

Whether we realize it or not, every one of our characteristics is there for a reason. If your parents left you to your own devices as a child, you may be more independent and reluctant to ask for help. If you were bullied as a child, you may have a soft spot for victim characters and be afraid to speak up for yourself. The point here is that your character pretty much can't be/act a certain way without an explanation. So they're an emotionless warrior. Why? What happened to them that made them this way? Or what do they fear will happen to them if they don't act that way?

For example, Bellamy is so protective over Octavia because his mother told him when he was six years old that she was his responsibility. He hardly had a life to himself because he was always trying to protect her. Also, he blames himself for her getting caught, so he doubles that protection because he believes that every one of her actions is his fault. 

In my own books, Ares from Fireheart is standoffish toward everyone because he doesn't have the proper social skills to make friends. He grew up relatively alone and is hated by nearly all of the delinquents, so he tries to deflect his pain and hurt them before they can hurt him. Fallon from Conflate constantly puts herself in danger for her friends because she grew up with Clarke as her only friend. She knows what it's like to lose someone she loves and doesn't want to do it again, so she figures that it's better if she were to die rather than them. 

10. Give them flaws.

As Hannah Montana said, "Nobody's perfect." These flaws should have direct consequences for your character. A character without faults is completely boring and is called a Mary Sue. Also, do not make these flaws trivial things like "Oh no! I am too pretty and now every boy in the village wants to date me ): My life is so hard." That's a Mary Sue. I mean things like "I have a habit of calling others out for their mistakes but never own up to my own. I was raised sheltered and my parents always forgave me for everything, so I was never taught how to deal with the consequences of my own actions." 

Sometimes your readers won't agree with what your character does because of these flaws. That is okay. As long as your narrative reflects these as flaws and not "the OC is always right and shame these characters for being mad at them", people don't have to agree with them all the time. It's also better if your character recognizes their faults and tries to fix them. 

You can absolutely make a character with questionable morals and make it work. HOWEVER, in order to succeed at this, your character should still have some type of emotional growth over the course of your story (exclusions include sociopaths and psychopaths because they have limited/no emotions, but they can still develop). Your character should not be flat throughout your book and just keep all of those same questionable morals. 

A canon example is Murphy. He's been proven to always do anything to keep himself alive, but he also cares deeply for his friends, most of whom he has tried to kill at some point in the past. Murphy has learned how to care for those around him while still being a cockroach. 

11. Have them lose some battles.

One annoying trope in fanfiction is when the character never loses a battle. They always come out on top of every fight and usually with little/no injuries. While it is entertaining to have a badass OC, it is highly unlikely that they will never lose at one point. Have them get beaten down and bruised. Have them get blindsided and tricked. Force them to deal with the consequences of their wrongdoings. Make them fail to achieve a goal. 

Failure is something everyone experiences and it's a part of being human. Some of the best lessons are learned after you fail because it's so shameful that we are unlikely to forget it. 

12. Have some relationships take a turn for the worst.

Have you ever had a falling out with a friend? What about a family member? In some fanfics, the relationships between characters never go sour. Give the audience angst! Some huge examples in my Conflate series are Fallon's relationships with Finn, Clarke, and Octavia. She starts off liking Finn but soon dislikes him when he constantly interrupts her time with Clarke and when she finds out he was cheating on Raven. She and Clarke often clash due to their conflicting personalities. As for Octavia, well... Fallon is a pretty nonviolent person and 3x10 O is... not. 

Having some relationships dip into that awry territory, even for a little while, can make the dynamics seem more realistic because not every dynamic is perfect all the time. You can fight with your friends. You can make up. However, some relationships are unsalvageable and that's a fact of life. Some wounds cut too deep to forgive. 

13. Give them habits. 

This is another thing everyone has. Whether it be a nervous tick that comes up consistently in the book or a random one such as biting their nails, giving your character some kind of habit will make them so much more realistic. Ideas include a specific routine they have to complete every morning, pulling their hair, bouncing their leg, biting their nails, picking at their nails, clenching their fists, tapping their fingers, clenching their jaw, constantly losing track of time, spacing out, etc. 

Here are some graphics from Pinterest if you want to screenshot them:

I hope you guys found this useful! If you have any questions or ideas to add here, feel free to comment them :)