A person who lacks humility cannot improve their leadership skills because they don’t acknowledge their own weaknesses and can’t work to improve them. On top of that, they won’t bring someone onto the team to offset their shortfalls.
Everyone else can get better, and while you might not be able to transform an awful leader into an excellent one, you can certainly coach a bad leader to become a better leader and a good leader to become an outstanding one, regardless of how they’re born.
“Usually people with the biggest egos are the ones who need the most coaching.”