He has mastered a 'formidable' amount of material.
The mountains were a 'formidable' barrier.
a 'formidable' enemy/opponent/weapon
(..) Dialogue: Marked=..,Default,NTP,!Effect,Then again, maybe some of you have\Ncome to Hogwarts in ... Dialogue: Marked=..,Default,NTP,!Effect,...possession of abilities so formidable that\Nyou feel confident enough... Dialogue: Marked=..,Default,NTP,!Effect,...to not pay attention. (..)2001 Harry Potter and the Sorcerer's Stone