noun
clenched fist; iron fist
Refers to a tightly clenched fist, often with a nuance of strength or readiness to strike. Can be used literally or figuratively for harsh enforcement.
彼は怒りで鉄拳を握りしめた。
He clenched his fist in anger.
その教師は鉄拳制裁で知られていた。
That teacher was known for his iron-fist discipline.