The answer is Darkrai.
Here's why:
* Master of all things bad: Darkrai is a Dark-type Pokemon known for its nightmares and dark powers. It's often associated with negative emotions and darkness.
* After: This implies a sequential relationship.
While there's no official Pokemon hierarchy where "Master of all things bad" is a defined position, Darkrai's nature fits the description well.
Let me know if you want to try another riddle!