Ultraman S01E21 - Space Directive M774

After sightings of a monster in Lake Kitayama, the SSSP investigates. Professor Nakayama, secretly grew the beast which now dwells at the lake's bottom. In a stunning turn of events, it is discovered that the doctor is not who he claims to be. He threatens to feed Kubo and Ide to his monster, but is instead trampled by his own creation. Ultraman defeats the monster with Ultra Slash.