Contrary to how it may seem, this achievement is storyline related and not missable. However (and this is why I'm writing this guide) DO NOT panic or assume it's glitched if you beat the final boss and credits start to roll, and you don't have your achievement yet!!! Much like the Marvel movies of late, there is a post-credit scene (which you will still get if you skip the credits by holding the back button) which will unlock your last bio, pertaining to a surprise cameo character. At the end of, or shortly after, this scene your achievement will pop.