This is an NPC, or a non-player character.
In-Game Description:
Special Event: Dr. Destructo Attacks! Defeat Dr. Destructo!
Description
@Dr. Destructo appears on a special event where players have to punch @Dr. Destructo in order to defeat him. @Dr. Destructo holds a Destructo Ray. @Dr. Destructo's gametag is highlighted in red, and it is either AI-controlled or a mod is playing in an account as @Dr. Destructo, to feature on events. Keep in mind that @Dr. Destructo could escape after a short period of time because it is an event.
Achievement
When @Dr. Destructo gets defeated. All players in the world will earn Superhero achievement.
The Fight
@Dr. Destructo can shoot out Public Lava that act as normal lava, but anyone can break it, like a Combusted Box. If a player is shot by his Destructo Ray they will be frozen in place for a few seconds. @Dr. Destructo has health messages that pop up when he is damaged, but it will quickly regenerate to 100% if he is not kept under constant attack. You can defeat him by punching him.