While we don't know the full background of Major Susan Turner (Jack Reacher: Never Go Back (2016)), we know that both Maria Hill (Marvel Cinematic Universe (2012-2023)) and Dex Parios (Stumptown (2019)) were both born into dysfunctional families and those three ended up in the military one way or another. The roles we saw were the result of twists and turns that happened during that time.

We all know MCU sucks when it comes to backstory, but (comic) canonically, Maria Hill's mother died giving birth to her and she grew up in an abusive household with her father. She joined the Marine Corps later in life.

Maria Hill was the outcome if they were offered a "better" option—an out. She joined SHIELD and due to her determination and skill, she quickly climbed up the ranks to the point where she became the second in command (even director at some point in the comics).

Dex Parios, undoubtedly, was the most "unserious" character compared to the other two. Though, she was more like Maria than we realized. Her growing-up life was somewhat alright compared to Maria's, but she did have to see the love of her life betrothed to another. Just like Maria, she became a marine—a damn good one.

However, unlike Maria, Dex was never offered a "better option". She had to see the very same man that broke her heart killed in front of her and for years, she blamed herself for it. She never had a "better option" because her mother then left her little brother alone, making her the sole caretaker of him. Dex was never offered a "better option" so for years, she had to hop between one job to another, trying to stay afloat, and was left to cope with her trauma by herself. Only years later, she finally found what worked for her: helping people by becoming a private investigator.

Compared to the other two that I listed, we know a lot less about Major Susan Turner, but I think we can make some guesses from what we saw. Another difference was that she joined the Army rather than the Marines, and she never got out. She didn't really need to (at first, at least).

The life in the army was treating her well. She was a well-respected commanding officer. She was damn good at her job. That being said, she never let her job get in the way of her values and despite all the conspiracy and shits they tried to throw at her, she ended up back in her job due to her resilience. Major Susan Turner is what they would've been if they stayed in the military.

In conclusion, idk if my writings did justice to explain it, but they were more similar than we (I) realized. They were all resilient, determined, stubborn af and didn't know when to quit. They were good people (some is more morally gray than the other) who used their very similar skills to help other people in the way they knew. I love them all, and I love Cobie for bringing them to me and doing justice to their characters.