I have been of the mind that I would have loved to see Dem and Rand have a quick battle then begin talking by all accounts Dem is and was a good man at heart, with Rands new look on things an apology could have tilted him back just to have Taim kill him in a " I was told to watch you Moridin said the Great Lord never fully trusted you, you who came to him last, you who always kept your hands clean with the excuse of all you want is LTT" I feel something like that would have been awsome he's was sold as the almost everything it seems fitting

Demandred was one of the Shadows foremost generals during the War of Power. In addition, he has millions of deaths on his record. I think that is a little different than keeping his hands clean. Also, his entire motivation for going to the shadow was hating Rand, and holding a grudge for more than 3,000 years doesn't make it seem like he'd listen to reason, even if he were sane. It would be nice, but it is extremely unlikely.

The Night Angel Trilogy by Brent Weeks.

I can think of several scenarios, but my personal favorite is this:

Demandred realizes that Rand went to Shayol Ghul, and so Demandred actually attempts to follow him, traveling to an area nearby the battle at Shayol Ghul, because travelling in there would be suicide. As he approaches, Demandred runs into Fain, and he has some form of cataclysmic three way fight with Padin Fain and his crazed minions and the Light armies. Even with Mat bringing the forces from Merillor to help, the Light has almost no chance. Fain Mashadar's most of the people in Demandred's circle, and almost ends up getting Demandred himself by using his own circle of 72 against him, and he manages to destroy sakarnen/blow it out of Demandred's grip. In the last moments, as he is distracted with killing Demandred, Fain is stabbed in the back by Mat. Demandred, now weakened, is brought down by other circles/flees.