I would say the final episode of Scryed.
It's a bit sad to know the end without the rest ;)
During the rest of the series kazuma only has his right arm 'in a suit' created by his power, and the other, Ryuho, fight by procuration, his power creating some sort of puppet.
In the last episode they both use their power to 'create' a suit, and fight.
As per Wikipedia:
Kazuma and Ryuho start fighting forcing one another to reveal their stronger Alter powers. Kanami and Mimori find them, but the former tells the latter the two have a strong reason for this fight. As the two fighters draw their final forms they nearly leave the planet. However, the two later return to the Lost Ground where they continue to fight with their bare hands. As one of them appear to claim victory the screen fades to white. In the epilogue, an older Kanami awaits Kazuma's and Ryuho's return.