The King of Evil in the Tower of Evil.
The King of Evil is the boss in the Tower of Evil in the Denpa Men series. To get to the Tower of Evil, you must defeat the Wolfbear boss who is guarding the Tower of Evil's entrance.
The Denpa Men: They Came By Wave
In the Denpa Men: They Came By Wave, the King of Evil is on the top floor of the Tower of Evil. To get to the Tower of Evil, you have to complete Digitoll Cave. The King of Evil has another form called the Great King. Great King is at the end of the Dark Ruins. To get here, you must acquire the Dark Orb, otherwise you are not allowed in. After defeating the Great King, you rescue Crystal.
The Denpa Men 2: Beyond the Waves
The King of Evil lies at the Tower of Evil, guarded by Wolfbear at Digitoll Cave. To reach Digitoll Cave, you must defeat the Hammer Angler, who lies at Ocean Tunnel. After defeating the Hammer Angler, you are able to get to Digitoll Cave. After beating Wolfbear, you reach the Tower of Evil, where the King lies. After defeating the King of Evil, you move on. Later in the game, the King of Evil makes several appearances, such as being murdered by the Evil Witch.
The Denpa Men 3: The Rise of Digitoll
In the Denpa Men 3, there is a mud ball named Squelch, who is the main antagonist of the Denpa Men 3. He stole Crystal, then before the Denpa Men arrived, Squelch gave Crystal to Sleeky Serpent, then Sleeky Serpent gave her to the Order. Eventually, when the Denpa Men find Squelch, he turns to True Squelch after absorbing the power of the Dark Orb. SPOILER ALERT: After defeating him, he evolves into Master Squelch. Eventually, once you get to Squelch's New Home, you find strange party guests, who turn out to be enemies. Almost all of them are Level 99, so I'd recommend you reach lvl 90+. Once you get past the enemies, you find Master Squelch. You find out he wants to fight and after taking about 5k damage, he turns into the King of Evil. This guy has 17,000 health, considered the highest health of all time in Denpa Men boss history.