He has mastered a 'formidable' amount of material.
The mountains were a 'formidable' barrier.
a 'formidable' enemy/opponent/weapon
(..) Oh, screw you, you big, green asshole! I'll do it myself! Hulk, we got a lot to figure out, pal. I thought you were formidable, machine. But you're dying, like any man. Get outta here! Go! (..)2018 Avengers: Infinity War