Giant Pistachion

The Giant Pistachion is a supporting antagonist of the Milo Murphy's Law episode Fungus Among Us and the hour-long special The Phineas and Ferb Effect. He is a Pistachion known for his gargantuan size and his deadshot eyes.

Fungus Among Us
The Giant Pistachion, along with his fellow Pistachions, were created by Derek following the latter's travel to the year 1955. Determined to avenge his deceased father King Pistachion, Derek formulated a plot of changing the timeline, allowing the Pistachions to take over the world in the present, rounding up all humans.

The Giant Pistachion was first seen spotting Milo Murphy, Orton Mahlson, Balthazar Cavendish, Vinnie Dakota and Diogee while hiding under a Cardee Boy mascot statue. After revealing himself, he tries to kill the heroes, but they end up outsmarting him by cuffing him with a barrel and a chain on one of his hands. This allows the heroes to escape, much to the Giant Pistachion's distraught.

The Phineas and Ferb Effect
The Giant Pistachion was seen again as he was freed by Derek, who summons him to kill several more of Milo's friends. However, upon witnessing the brutality of the battle between the humans and Pistachions, the Giant Pistachion decides that he has enough and leaves the scene, determined to make himself a better person, much to Derek's annoyace.

The Giant Pistachion is last seen serving a soup kitchen for several people, that is until he realizes too late that he and the other Pistachions are being erased from existence (due to Heinz Doofenshmirtz creating a time machine to transport Orton back to 1955 to kill Derek).