(This amuses me. Harry's gonna kill him, so Voldy sits down and writes a letter to him.)
I have had my war and lost. It is not you who have won, however. Perhaps the world has won. Perhaps no one.
My Death Eaters may be taken to Azkaban, now, and what you call suitable guards will watch over them day and night until their deaths. What will this accomplish? Will you have brought world peace, Harry Potter? Will anyone see what you have done?
There will be another Dark Lord following me, and although you will be remembered in legend, do you think that I will be forgotten? My spirit may linger and haunt you for years. Now you are a murderer - a murderer of a murderer, true, but you have killed and blood is on your hands. Will you be glad to imagine my followers rotting in death in your prison? Will that satisfy you? You and your friends and these people who you call your own saw this path for you, this path to kill me. I wonder what other paths might have been. You could have been in Slytherin, Harry Potter, and perhaps this would have turned out the same. Now that you know the truth about your parents, now that your mentors are gone and your school is gone, what will you do? Will you rebuild Hogwarts from the ashes, raising a new and better school? Will there be students who will come to your Hogwarts to learn on the foundation of what the Dark Lord destroyed?
Know only this, my killer. Know that there will be another. Know that peace is not upon you. You cannot live in peace. Know that there may always be a betrayer in your midst. Not all of my followers were known, and you are a fool if you think they are. Walk lightly, Harry Potter, because our fight will haunt you for years. It will never be over for you.
(signed with the Dark Mark scrawled in black blood)