As I plan my Tankmen webseries, I was reading Captain John's personality descriptions according to @JohnnyUtah and the Tankmen Wikia.

https://tankmen.fandom.com/wiki/Captain?so=search

We have a smart, fearless leader who has a feminine side.

Self-proclaiming himself as a mother and being a fashionista, he has some femininity.

But what's missing are weaknesses, while we can't count his feminine side (he's clearly not ashamed of it), I identified one weakness and fear John has, the colonel....

Yep, this guy...

I identify this tankman as the colonel because not just his insignia but there's artwork of him barking at John like he some authority over him.

He looks pretty pissed here!

John fears the wrath of the big cheese, the head of the military base he works for. While it's clear the colonel is not always present on the battlefield, critiquing those beneath him, I think we know where the colonel is when he's not present....

Looking for excitement. (It it is the colonial because if you look closely, you can see the insigna on his left shoulder) (Maybe he watches the Thugmen's games a lot in his office)

Imagine if John saw him at Frank's?

He'd be shaking in his boots. (And I bet if the colonel just casually greets him he becomes very avoidant like "Oh no, it's the colonel, he's going to try to find one thing wrong with me and kick my a** for it.")

We can confirm he's entirely fearless, he does have a fear, the colonel.

So, in my webseries, I will make this fear into an insecurity, wanting to please authority figures. Where John fears he's never good enough in the eyes of his superiors, especially the colonel, even if he's doing a fine job. Where he believes there's standards that are too high to reach, even if he's following those standards. And we will see he just wants to make the colonel happy no matter what he does, and even if he's told he's doing a good job, he feels it's not enough.

I think that weakness matches up with John being a military captain and adding this weakness will make him feel more human. Where he thinks his superiors have too high of standards, higher than they really have.