I need help on stage 27... the fight with the ZOnuda Robot.. he keeps making all my units disappear.. and when his hp is low after being hit by my star gaogaigar.. its GAME OVER.. help...

Okay, this stage had me confused, too, but I eventually passed it with much frustration.

The key difficulty is the fact that attacking or being attacked by the Mitoko-Zonder (the enemy) causes any unit other than GaoGaiGar to retreat. If GaoGaiGar attacks, one of its pilots for that stage is destroyed (not permanently, don't worry!).

The solution is to use your character's seishin. Since they're just going to disappear after the attack anyway, lure the enemy close (if none of your units are in its threat range, it'll head toward GGG). Once it's within range, have one of your attackers use Hot Blood (2x damage), and Sure Hit (100% Accuracy) or Focus (+30% Accuracy/Dodge), and hit it with the best attack you can. Do the same for every unit aside from GGG. If you can kill it without attacking with GGG, great. If not, use the seishin on GGG and finish it off. The Game Over occurs if GaoGaiGar attacks or is attacked by the enemy six times if my count is accurate.

Once you reduce it's HP to zero, GGG will automatically finish it off, and you'll enjoy the cinematics til Chapter 28. Hope this helps!

I once found that Nadesico was attacked by the enemy, but it didn't retreat. Isn't this information quite useful?

Huh, how about that. I never really attacked with my mothership units, I just used 'em as big loading docks. Neat.