Nasty Plot Dark TM

Found in Area Zero. From Research Base 2, and after regaining the ability to use Koraidon/Miraidon, climb up the wall behind the center, and up another wall to find the TM sitting on a grass ledge above.

Inside small cave accessible near the initial bus stop.

Whose bright idea was it to place it on top of this pillar?

You can super jump or glide from the cliff to the east. Or fly up.