Ben 10 season 2 episode 5 : Grudge Match

Diamondhead battles the still-mutated Kevin, who had rendered Gwen and Max unconscious. A droid named Slix Vigma observes their fight, recognizing them as potential gladiators. Amidst the combat, a teleportation beam takes Diamondhead and Kevin to a huge ship called the Mega Cruiser, where life or death gladiator matches are regularly held between slaves captured from different alien races. There, Vigma makes Ben and Kevin a team, bonding them with shackles that transfer pain from one to the other. With no choice, Ben and Kevin battle another captive, Technorg, during which Ben teaches Kevin new attacks combining Omnitrix alien abilities in order to win. Though Kevin intends to kill Technorg, Ben restrains him and spares his opponent's life. After the fight, Ben and Kevin rally the other prisoners, who nearly all escape. However, Kevin traps Ben with the intent to kill, revealing that he still bears a grudge. Ben transforms into Cannonbolt, the only alien Kevin doesn't have, and knocks him out. Cannonbolt was about launch his escape pod, until Kevin regained his conscious and tries to seize Cannonbolt. Fortunately, Technorg abides by a code of honor and saves Ben, sending him back to Earth. Kevin is left aboard the Mega Cruiser with Technorg.