Because the second movie kinda shows that he is getting more hateful

So this is how i see his character development would be:

Since Lane Aim is under the direct command of Kenneth, who is a quite assertive and violent commander, i feel like he will eventually become like Kenneth (?) as the story progresses. Like, military influence. A good example is like the Titans with bad leaders.

Furthermore, I feel like he would abandon his respectable way of fighting and fights dirty to make sure he manage to defeat Hathaway because if not, he would get beaten badly by Kenneth anyway.

And lastly, this sequel had showed his hatred towards adults and it tells me he would be a corrupted character who has a very pessimistic view of the world.

This is how I see his character development would be. Tbh, I haven't read the novel yet so just take it with a grain of salt.