To earn this achievement, you'll first need to learn the skills "Mind Control" and "Throw Weapons". Make sure you have the difficulty set to Medium or above, anything below this difficulty and the fights will be too basic.
You'll need to keep arranging fights either via the "Arrange Exhibition Match" from your Legate or Magistrate, via a Pit Fight or via the normal means. You'll need to make sure your opponent is chained in order to make this easier on yourself; you could attempt it via a normal fight, but having the enemy chained is a lot easier.
When you're finally up against a chained enemy, simply use the F key to throw your weapon at your adversary. You can pick your thrown weapon back up to repeat the process until your enemy is defeated.
Having the game difficulty set to Easy won't allow for chained enemies.