If Gate Gate is recited to remember the the path to enlightenment via emptiness, then it's opposite would be Om Purnamadah, which is the path to enlightenment via fullness:

All this is full. All that is full.

From fullness, fullness comes.

When fullness is taken from fullness,

Fullness still remains.

Other translations will use 'infinity' or 'perfection' or 'Brahman' just because the word purnam itself is extremely common, just meaning all of something.