Dieter

Dieter was, as far as anyone's really concerned, the main antagonist of Bowser Jr.'s Journey, a bonus game included with the 2019 remake of Mario & Luigi: Bowser's Inside Story. He was the leader of the BFF, an organization that pretended to be a drug company offering a cure for the mysterious Blorbs disease called the Best Fitness Friends. In actually, the BFF was the Brute Force Federation, a unit of Fawful's army tasked with eliminating the Koopa royal family. However, they failed, and were destroyed. The other leading members of the BFF were Kaley and Beef. They were killed by the Koopa Troop after they took their own mind-control drug, Malatone Formula X.

In Boo's Pizza, the BFF, referred to as the Brute Federation Force as a reference to Metroid Prime: Federation Force, return from the grave to get revenge on their enemies.

History
Dieter's first act is to test an improved Malatone Formula on an unconscious Jimbo. However, he is apprehended by Captain Boo, who accuses him of being responsible of turning Bowser into Dry Bowser at the end of Bowser Jr.'s Journey (in actuality, it was Bowser who overdosed on Skeletone Formula D, however it should be noted that Skeletone was created by the BFF as a counter to Fawful's bio-engineered Blorbs). Dieter retreats and is met by a surprisingly talkative Beef, who explains that he planned to purchase Robot Masters from Dr. Wily. However, Wily already gave them six or so. They are then attacked by King Dedede.

At a later point, as Bowser and company had left the Castle of Koopa to invade Gaia and later got caught up in Hyrule, the Brute Federation Force occupied the Koopa Kingdom. The mercenaries from TF2 stormed the castle, however as these posts were made concurrently with the 6 January 2021 terrorist attacks in the United States, the arc was abandoned.

Dieter would later team up with Sephiroth and Dr. Mario to do evil stuff.