Which prophet lamented over King Josiah after his death, according to 2 Chronicles 35:25?

Answer: Jeremiah

All Judah mourned Josiah. Jeremiah lamented over him, and the singers' laments for Josiah became a statute in Israel.

“Then Jeremiah lamented over Josiah, and to this day all the male and female singers recite laments over Josiah. They established them as a statute for Israel, and indeed they are written in the Book of Laments.”— 2 Chronicles 35:25 (BSB)