'Isn't it good to know that Ender can do the impossible?'
This shows that throughout the book Graff has been a little bit unsure that Ender was the one. When Ender killed the giant, Graff shows relief and appreciation.

'We're trying to save the world, not heal the wounded heart. Your to compassionate.'
This shows that Graff is compassionate to Ender even though he doesn't show it to him.

Desperate, lazy and compassionate