This character is one of the main in the story. He plays an important role in the dynamics of the book. But first things first.
He is a friend of Henry and is involved in story-telling just to show who a person should not be. Ettore isn’t dynamic; he ends up staying the same person he used to be in the beginning.
He didn’t have many lines, but he has a lot of descriptions other characters made about him. Henry likes Ettore for his brave but totally dislike because of the behavior he does.
Ettore is an Italian-American soldier in the Italian army, and unfortunately, he boasts of his medals and rank while insulting others. He is very quick to instigate a fight or display the medals that he claims to have worked so hard to win, he believes in and pursues the glory and honor. And that is one of the main reasons why Henry doesn’t like his behavior. Because in this regard, he is the opposite of Henry, who does not care at all about personal glory. The only thing he cares is a blessing and benefit of things he does.
Why the author of the text uses him in the text if he represents only bad qualities? Exactly because of this reason. Everything is relative. How could we know that Henry is a good character without knowing a bad one? Without people of a bad character we would live in utopia, and this, as you know, is an absolutely absurd world.
Ettore Moretti in the Essays