Well, he's constantly using his power, so probably no. But he's been close before. It's never really stated when he is at or near full power as much as it is stated that he is weak or low on power. From what I have seen, for him to reach near full power he would have to feed much more than he does usually. 
 
The only real examples I can think of is when he knew him and Tyrant were going to go at it he began preparing himself. After Annihilation we get to see how much he needs to consume just to get back to normal, so that is probably the pace he would need to go when trying to gain his max. He might have been at full power when Frankln and Valeria brought him from the heart of Eternity though.

Full power?  Probably not.  
 
Well-fed is another story though, though in this state he isn't devouring worlds so he tends not to fight when sated and thus his typical strongest. 

There is no fully powered Galactus. He can't exist given the showings he's had. There is no limit to how much he can devour.

Well, he's constantly using his power, so probably no. But he's been close before. It's never really stated when he is at or near full power as much as it is stated that he is weak or low on power. From what I have seen, for him to reach near full power he would have to feed much more than he does usually.   The only real examples I can think of is when he knew him and Tyrant were going to go at it he began preparing himself. After Annihilation we get to see how much he needs to consume just to get back to normal, so that is probably the pace he would need to go when trying to gain his max. He might have been at full power when Frankln and Valeria brought him from the heart of Eternity though.

I hope he is at full power now.  When you pursue an invasion of Asgard, you better be ready.  No excuses.  This could be the fight of  the century.  Or maybe it will leave us,  the readers hungry for more. With a Galactus appetite. 

@powerherc:

Yeah Galactus would be very powerful but not living tribunal and certainly not beyonder level of power.

Lifebringer is basically a full-power Galactus; he pretty much just stomped Chaos and Order in Ultimates 6 but still is much weaker than Molecule Man (but that's not saying much since him and Reed are the two most powerful beings in the omniverse now).

I think he was close to full power when he fed on 4 planets and was able to oneshot a celestial.