He has mastered a 'formidable' amount of material.
The mountains were a 'formidable' barrier.
a 'formidable' enemy/opponent/weapon
(..) on the day of my birth. Before a Romulan ship attacked the USS Kelvin. You know that, sir. I've read your dissertation. That ship, which had formidable and advanced weaponry... was never seen or heard from again. The Kelvin attacked a place on the edge of Klingon space. (..)2009 Star Trek