The word underdog is not a biblical terminology, but it should have been. Starting from Adam, especially after the fall, if it wasn't for God's compassion, no one would have a chance at survival. We are all underdogs, one way or another, but this is the story of characters like Gedeon, Hagar, the prodigal son, and so on.
And if you look a little closer, you will see that these stories are your stories. You will see that there is hope for you. When people dismissed you, do not dismiss yourself because inside of you, there is a Jephthah whom God is ready to lift up.
Maybe you are dealing with a situation, and you see no way out, but I promise you there is a way. Read on, and you'll find out that God is still for the underdog. He is for you.