This is how I'd kill Abbaddon. Challenge him to personal combat (you would need someone famous like an Inquistorial Lord or Chapter master with a company of Terminators) and get him to accept. When he's on the surface of the world, send a Execution Force to disable his teleporter capabilities of his ship by getting on board. While he's killing whoever you sent, order an Exterminatus while you activate plyons to block the Gods from getting him. CHance of success is 45% but it's worth a shot. Also most of these components would be hard to obtain.