Pierce Brown
It feels more important to comment on the entire series than on just the final book. But Pierce did a great job combining all of the plots holes. The only critique I would have is there seemed to be a massive amount of plot armor around the top characters. Slight spoilers here but the whole takeaway in my opinion from the first book was how small the "academy" was compared to the rest of the universe. But then in the 2nd and third it felt like every best character, toughest enemy, etc all came from the academy. It just felt like there was too much emphasis on the characters built in the first book and missed out on the opportunity to really make it feel like the academy was only a small slice of the real thing.