Who was Johanan in the Bible

Johanam was the one who pursued the assassin of Gedaliah, killed him and rescued the Judean captives.
When Johanan son of Kareah and all the army officers who were with him heard about all the crimes Ishmael son of Nethaniah had committed, they took all their men and went to fight Ishmael son of Nethaniah. JEREMIAH 41:11–12
We are all gray. As difficult as it is to accept, the truth is that every human being is always capable of both the most noble and the most heinous of deeds. Johanan was no different.
When the Babylonians invaded Judah and carried away most of the nobles and other leaders, Johanan was among the “army officers and their men… still in the open country” (Jeremiah 40:7) who escaped
capture. The Babylonians appointed a man named Gedaliah as governor over those who remained in the land, and Johanan and the other captains agreed to submit to Gedaliah’s authority.
When Ishmael, who was one of the captains, assassinated Gedaliah and took other Judeans captive, Johanan courageously chased after him and rescued the captives (Jeremiah 41–42).
Immediately after this heroic deed, however, Johanan and the other leaders made plans to flee to Egypt to escape the wrath of the Babylonians over the assassination of Gedaliah. They consulted the prophet Jeremiah, who warned them not to go, but they chose to disobey the Lord and go anyway and they took Jeremiah with them. It is likely that they died there, just as Jeremiah had prophesied (Jeremiah 42:15–16).
If we truly understand that we are all capable of the best and the worst of deeds at any time, then there is no room for judging others nor is there any room for pride. We are no better than anyone else, and no one else is any better than us. We are all sinners in need of God’s grace (Ephesians 2:8–9).