When Harry hit Bellatrix with the Cruciatus curse, you could see fear on her face even though she wasn't yet in pain. Despite his kind nature now, I imagine Harry will kill and torture without remorse in "Deathly Hallows." If anyone deserves revenge it's Harry, Neville and the Weasley family.
And who knew Aunt Petunia has such hot legs?
Not I!
Remember, Bellatrix said you had to mean the curse, and also enjoy it.
It made me wonder if we've ever seen any of the good guys use an unforgivable curse successfully. Snape used Avada Kedavra on Dumbledore. But in the rest of the battles, were our guys using those curses?
I'm not sure any of the kids are up to it, even Harry.