Alright since Joachim is so prideful that he can win anything he will give 5 free turns to attack him will actually 6 since he gives you another free turn. First of all you can only use the attack command so the Coral Lariat will be the best recommened since Kieth's hit areas are so narrow. A couple attack raising equipment will also be good as well, and before you believe your doomed after the 6th turn you still have a chance that all his attacks will miss. Just keep hitting the areas and he will go down.