DYNASTY WARRIORS 9 Empires

This will most likely be earned in your first battle as you will have no secret plans available/unlocked, all you have to do is win the battle for the achievement to unlock.

If you do somehow have access to secret plans on the first battle then just select the option to not use a secret plan and win, if the enemy uses a secret plan then this will have no effect on the achievement, you will still get it at the end of the battle (make sure to foil their secret plan to gain progress towards other achievements though).