Answer:
Dear Fortunato,
While I know that you are dead, I would still like this to be addressed to you, for you are the only one whom I can confess to truly without getting hurt, and I promised myself that I would not get hurt during any of this.
As you may know, I have killed you. No, I did not do it from act of impulse, or for a laugh. I'm sure you know exactly what you did that made me enclose you in that small space, left there to rot and die. You have insulted my name for the last time. You have hurt my pride, and I am done suffering in silence due to your words.
So please forgive me for what I have done. I just wanted you to pay for your actions. It was for your own good, really. For you do not disrespect a Montresor and get away with it. Had it been anyone else, they might have done the same thing, I suppose.
That fateful night that you were walking home from indulging yourself in drink, after I had thought of my plan and how exactly I would execute it, you had drunk much more wine than was good for you. If I hadn't acted fast, you might have just drank yourself to death and I would not have been able to get revenge, but thankfully that did not happen before I was able to get that last stone secured into the wall, and place every bone back the way that it was before.
Thank you for having been compliant, and so easy to lure. It would have been much harder had you not complied so easily, or asked too many questions. It made my life much easier. I hold Luchresi's name above your head and you pounced on the opportunity to gloat your skills of wine testing. To be truthful, though, you don't know one wine from another. Dear Luchresi knows better than you ever would.
Did I not tell you that we should have left? If you knew what was best for you, you would have turned around the moment we got down into that dank, cold vault. Had you not been drunk, and after noticing the amount of bones that may or may not have been my family, you might have turned around quicker. But no, your pride could not let Luchresi surpass you, for you are too proud for that.
Well, I believe that is all I needed to say. That was the last time you ever disrespect my name, and I truly hope you have learned from that mistake in the next life, or else you will suffer the same terrible fate.
Sincerely, Montresor