We hardly need to ask who this Judah was. Not only was he the fourth son of Jacob and Leah, but Judaism and Jews are named after him.
At several critical junctures it is he who was the leading spirit amongst the brothers. It was Judah who tried to save Joseph when the brothers wanted to kill him, Judah who persuaded Jacob to let Benjamin go to Egypt, Judah who led the negotiations in Egypt with the brothers.
So important was he that the Torah speaks of “Judah and his brothers” (Gen. 44:14), and Jacob supported this idea when he blessed his sons and singled out Judah for praise (Gen. 49:8-10).
The Midrash even calls him the king of the family and points out that his name comprises the four letters of the Divine Name plus the letter dalet, the fourth letter of the alphabet, because he was the fourth son.
Yet Judah was no saint. His sins as well as his virtues are written up in the Torah text. The way he treated Tamar did not redound to his praise, though the sages give him credit for admitting his sin and repenting, and from his union with Tamar derived King David and the royal dynasty (see the end of the Book of Ruth).
Judah is the prototype of the leader who does great things but can lose all credibility unless he is man enough to own up and seek forgiveness.
A leader who brazenly tries to get away with misdeeds comes crashing down in the end with his/her reputation in tatters.