Looking for a sci-fi military book with a male lead that undergoes character growth through the story

As said in the title, I am looking for a book whose story takes place in a futuristic setting and where the main character is part of the military or gets recruited at the start of the story. I want the male lead(mc) to start of as kind of a douche bag, not actively malicious or annoying but someone who is spoiled and lacks self awareness. I want him to grow through the events of the story and become someone whom others can rely as he rises up through the ranks.

It would also be nice if the story has a romantic subplot where the main love interest also contributes to the male characters journey along side his personal growth and isn't some wallflower. Though I like romance as a subplot and not if it detracts too heavily from the story which I hope will include themes of friendship, war, tragedy etc. A book series will be pretty rather than a single book would be appreciated as it might allow for a better paced story. I am a book newbie and am looking forward to your suggestions..