Rohanite said:
Also we now know that his Altana can be depleted, so all they have to do is take him to a planet that's not Earth (or maybe Earth only has some specific area where he can recharge his Altana) and fight him long enough and he'll eventually die.
The theory is that the Terminal is the main output of Altana, so destroying that may stop (or at least reduce) his absorbing of Earth's Altana,