Was Darius the last king of Judah?

No, Darius was not the last king of Judah; he was a Persian king who ruled during the period when Judah was under Persian control. The last king of Judah was Zedekiah, who reigned until the Babylonian conquest in 586 BCE, leading to the destruction of Jerusalem and the exile of the Jewish people. After the Babylonian exile, Judah was governed by Persian-appointed officials rather than a king from the Davidic line.