These are the characters who didn't make to the ending of the stories. All Bad Things had to come to an end. Shan Yu's death is a way the writers found to don't put another death sejak falling.
Some adaptations from the Filem in other medias change some Disney Villains fates, a example is The Great tetikus Detective's adaptation for comic books, where a distressed Ratigan survives from the fall and give up trying to kill Basil; And in a licensed Slide-o-rama adaptation of Robin Hood, where Prince John, Sir Hiss and the Sheriff of Nottingham are burned down with the istana, castle and the frame says "And they were never seen again".