Frifle's Challenges are by far one of the most tedious tasks in the game, but they can be made manageable using shortcuts. The hunts each want you to kill a lot of a specific type of enemy, but almost always that enemy can be isolated to a select few floors you can shortcut to and replay over and over again until you complete the hunt. Some of the hunts will also include bosses, and these can be easily done by playing through a Boss Rush, as that is guaranteed to spawn all of the main chamber bosses. If you have not yet unlocked the Boss Rush, use the shortcut technique with the chamber of that boss until you spawn them in, and then you can kill them for the hunt. If you have not yet unlocked various shortcuts, you can just play the game continuously until the hunt is complete, which takes a while but is completely possible. Using these methods, the 15 main hunts can be completed, which will unlock the achievement.