The trick is to attack him from two opposite directions, this way units on one side can shoot at him, while he is busy destroying the units on the other side.
That said you will still need a lot of units, at least two, better three full belts. Each attached to 4 factories. Also your units should have a strong weapon color he is weak against (idealy cyan or white). Unit armos doesn't really matter as the laser kills em all.
It also might be that the boss is still a little to powerful...