I can't think of a more fitting end than Tony having to take out Chris. For the entire series Tony has groomed Chris, loved the kid more than he loved most, and shown more patience with him than he would anyone else - Chris's death is inevitable.

"Fredo -- you're my older brother, and I love you. But don't ever take sides with anyone
against the Family again. Ever."

"My father taught me many things ... keep your friends close, but your enemies closer."

"I know it was you, Fredo. You broke my heart. You broke my heart."