He's a Skrull that can't shapeshift. He can absorb Gamma energy and empower himself. He's beaten Hulk twice I believe, Strange and the rest of the Defenders (Spider-Man, Shulk, Nova, Ms. Marvel) were unable to stop him. He has a healing factor that allowed him to regenerate his own head after he crushed it with his own hands. He's kind of an anti-hulk.