Daniel 2:33
its legs of iron, its feet, part of them of iron and part of them of clay.
Daniel 2:40-43
And fourth kingdom will be strong as iron, [and] {just as} iron crushes and smashes {everything}, and as iron shatters all of these [other metals], [so] it will crush and it will shatter [these nations].
Daniel 7:7-8
After this in the visions of the night I was looking and there was a fourth beast, terrifying and frightful and exceedingly strong, and {it had} {great iron teeth}, [and it was] devouring and crushing, and it stamped the remainder with its feet; and it was different from all [the other] beasts {that preceded it} {and it had ten horns}.
Daniel 7:19-26
"Then I desired to make certain concerning the fourth beast that was different from {all the others}--exceedingly terrifying, with its iron teeth and its claws of bronze; it devoured and crushed [and] stamped the remainder with its feet--