=== Ron, Hermione, and Harry are untouchable, I think, ===

The classic "bittersweet" resolution would require Harry to kill one of Ron or Ginny in order to defeat Voldemort, thus wounding himself and either destroying or clouding his relationship with his true friends for the rest of his life in the interest of the greater good. This would be heightened by having Voldemort just banished again and not defeated forever.

sPh