Which Assyrian king claimed that he could read difficult Sumerian texts?

The Assyrian king who boasted of his ability to read difficult Sumerian texts was Ashurbanipal.

Reigning in the 7th century BCE, Ashurbanipal was a highly educated ruler who mastered scribal and priestly knowledge. He is famously remembered for assembling the first systematically organized library in the ancient Middle East at Nineveh, which preserved a vast collection of Sumerian and Akkadian literary, religious, and scientific texts.12