Hero of Earth

A alien forces head to earth to destroy all humans. Humanity last line of deffence is a young man who lost his father in the first invasion. His father starts a work on two things a large Mech that can whip out a large fleet. Then there was a small Mech that was carried in it for single combat and take on invaders and their machines. He has lost so many love ones and friends he refused to get close to anyone. He has become the perfected fighter. He pushed the women he loves away and has signed to defend the planet at all coast. He has a rival pilot and company that thinks they can do better but they fell and he is force to save the pilot. Who is an old friend of his back when he was young?