na-adjective
fiercely strong; ferocious and powerful
Describes a person, warrior, or spirit that is both physically powerful and intensely fierce. Literary and somewhat dramatic; not an everyday descriptor.
彼は剛猛な武将として知られていた。
He was known as a fiercely strong warrior.
その剛猛な気迫に圧倒された。
I was overwhelmed by his ferocious spirit.
Compound of 剛 (strong, firm) and 猛 (fierce, violent). The exact historical derivation is uncertain, but the word is formed from kanji with clear semantic contributions.