Ancient King

The Ancient King (古代王, Kodaiō) was the king of the Terror Lizard Clan.

Appearance
The Ancient King is a colossal, loosely humanoid creature that has various animalistic features, such as scales, horns, claws, and a reptilian tail.

Personality
The Ancient King is a ferocious and violent being who wishes to take the surface of the Earth for his race, much like the majority of the other "kings".

Alien Conquerors Arc
The Ancient King awakens after 300,000,000 years of slumber, which was used to wait for the other kings to be taken out. He is attacked by military forces, but the missiles are proven ineffective against the Terror Lizard's skin. The Hero Association deploy Tatsumaki to take care of the threat.

After briefly conversing with Tatsumaki, he's killed by her, after getting smashed by a meteor brought from space by Tatsumaki with the use of her telekinetic powers.

Abilities and Powers
Not much was seen of his abilities, due to how quickly Tatsumaki disposed of him, however it can be assumed that his strength and endurance are tremendous.

Supernatural Abilities
Energy Projection: He seems to have the ability to charge energy beams from his mouth.

Physical Abilities
Immense Strength: The Ancient King easily bursts out of a mountain and it's safe to assume by its size alone that it's capable of causing a lot of damage.

Immense Durability: The Ancient King is seen easily enduring military missiles and also comments it would require something like a "meteor" to kill him, giving him amazing durability.

Trivia

 * His character design is based off of Godzilla.
 * Ancient King is the fourth of many "Kings" mentioned in the series, and the first one who is anime-only, the others being the Subterranean King, the Beast King, the Deep Sea King, the Sky King, the King of the Underworld, the Monster King, and the Forest King.
 * The animation team misinterpreted ONE’s intentions when animating the Ancient King fight. ONE only wanted Tatsumaki to drop a big boulder on Ancient King. Before the boulder hits him, Ancient King has a flashback of the meteor that destroyed his race eons ago and starts to scream. She was not supposed to pull a meteor from space. The meteor scene was supposed to be flashback only. If she could do that, she should be able to bring down Boros's ship without difficulty according to Murata.