Virtually all of the major charachters (and some of the minor ones) in Megillas Esther have a clear ending for them. Mordechai and Esther live happily ever after (sort of). Haman and his ten songs are hanged. Even Haman's daughter was declared dead by a midrash which proclaimed that she threw herself off a building after dumping trash on her father's head while Haman was parading Mordechai around.
But to the best of my knowledge, Zeresh just disappears. I would think there was some account of how she died, seeing as how she was the one who suggested to Haman about the gallows in the first place. Is there any account of what happened to her?