The minecraft hostile mob have all kinds of shape and sizes, but when you kill all of them, there's only one remain. . . And that is the ender dragon, then you kill it, Advancement get: Free the End. But there is one more advancement that didn't granted and that is monster hunted.
then i try:
1. Sort all hostile mob from A-Z
2. kill every single one of the hostile mob in my inventory
3. Two more hostile mob to go and that is the wither and the ender dragon
4. Killed the wither
5. Killed the Ender Dragon but the advancement doesn't showed up