Stream Underdog Online Free – Watch Full Movie from Home at 123Movies. . Boris "Kos" Kosinski is a top MMA fighter. In the biggest battle of his life with his greatest rival, Denim Takaev, he makes a mistake that destroys his entire career. He loses everything. This failure brings him through a series of ups and downs, but it also pushes him to undertake a titanic effort to fight and win back respect and love