First, make sure Abbot Jack of Alltrades is back to Alltrades Abbey. Next, go downstairs of the Abbey, and talk to the purple person standing in front of the Inn. He will give you the "Gladiator Graduator" quest. All you need to do is defeat a certain number of slimes with a Super High-Tension Dragon Slash. Dragon Slash is a MP-free ability that a few classes can learn, and to achieve Super High-Tension you must use "Egg On" on the same character multiple times. Note that when you are on a Tension of 50, there is 50% chance to successfully achieve Super High-Tension (Tension of 100). Just keep Egging On the same character until you achieve this. A quick way to finish this quest is to go to go to Newid Isle and repeatedly engage a battle with a Slime. Chances are it will not be alone. You must not let the Slimes merge into a Slime Stack or a Slime King, as only Slimes count for this quest. Use Snooze on every turn to make them sleep, keep Egging On the character with Dragon Slash, and use Dragon Slash when the Tension is at 100. You can easily finish this quest with only one battle, as most of the time three or more Slimes will appear in battle. Return to the Abbey, talk to the purple person again, and you will have access to the very powerful Gladiator Vocation.