What worked best for me, was using Echo Echo (the small robot form) and make two clones (press
twice). Let the clones attack Vilgax, and if necessary make new ones, if the other ones die. In the mean time try to get close to the red pipes, because as soon, as your clones beat him up enough, he'll charge at you and run into the pipe, getting hurt, plus giving you some health, if you stay close enough to the pipe. Now I moved around killing the minions as quickly as possible. Try to use your special attacks. (I guess you can chose an alien form of your liking, but I would go with either Goop -the slimey one- or Big Chill -the ice breathing, moth like form-) Once all minions are defeated repeat all that two more times.
If you do that, Vilgax is a joke and easily beaten.
Hope that helps!
New XBL Profile since October 30th 2013.
Completed Retail Games: 16
Completed Arcade Games: 18