Yakon is one of Babidi's henchmen, and the most feared creature in the universe. He is a gigantic insectoid monster with long claws. He eats light energy and comes from the Planet of Darkness.
Dragon Ball Z
When Vegeta destroyed Pui Pui without receiving any damage from him, Babidi sent Yakon to fight them at Level 2 of his spaceship. Two of his men went to get Yakon, but Yakon ate them both. Babidi spoke to Yakon and told him to kill Goku, Vegeta, and Gohan. Goku fought Yakon. Even when Babidi took them to the Planet of Darkness, where it was too dark to see, Goku had the advantage. He turned Super Saiyan so he could see in the dark, but Yakon ate his light energy. Goku transforms into a Super Saiyan yet again. Delighted by the fact that he has another meal, Yakon begins sucking up the light. Using Yakon's greed to his advantage, Goku counters by powering up to an enormous extent (involuntary showing Vegeta a glimpse of his Super Saiyan 2 power). Yakon is completely oblivious to Goku's plan and continues to consume Goku's light energy so much that he begins to inflate. With Goku providing him with so much light, Yakon violently explodes.
Dragon Ball GT
Yakon returned in Dragon Ball GT, where he escaped from Hell with other villains. Yakon broke through a wall and attempted to attack Goten, but he was quickly killed by Trunks to rescue his best friend. Yakon then was sent back to Hell.