Alien Metron

Alien Metron is an alien that as appeared as an antagonist in several shows in the Ultraman franchise, first appearing in Ultraseven.

Ultraseven
It first appeared in episode 8 of Ultraseven where it caused outbreaks of violence through tainted cigarettes it distributed. He was eventually found out by Dan Moroboshi, who transformed into Ultraseven and defeated Metron.

Ultraman Ace
Alien Metron's son, Alien Metron Jr., later appeared as an agent of Yapool. It fought Ultraman Ace alongside Doragory and both were destroyed by him.

Ultraman Max
Alien Metron reappears in Ultraman Max, where it attempts the same scheme it tried previously in Ultraseven. After being discovered and confronted by Ultraman Max, Alien Metron bids the Ultra farewell and leaves Earth in its ship.

Mega Monster Battle: Ultra Galaxy Legends The Movie
Alien Metron appeared as a member of the Belial Army. It fought Ultraseven alongside Eleking, Banpira, Alien Guts, King Joe Black, Verokron, Doragory, King Pandon, Fire Golza, and Nova to take on Ultraseven. It was destroyed by Ultraseven's Wide Shot.

Ultraman Ginga
Alien Metron participated in the Dark Spark War until it was turned into a Spark Doll by Dark Lugiel.