You might get this without trying. The only enemies that count for this, are the ones you get experience from. You cannot keep killing summoned enemies or ones that reappear when you don't move to the next checkpoint. Rolling away helps if you see an enemy winding up for an attack. Near the end of the game you will get an extremely powerful sword. Almost all enemies die in just one or two hits. This gives you ample opportunity to gain the achievement, especially on your final climb to the boss where there are lots of enemies spawning as you go up the stairs. If you don't have it by the time you beat the game, you may try it in the Tides Challenge or Time trials.
*If you're having an extremely hard time with this, and you can barely make it through the game on easy, then what you may want to do is find a checkpoint with very few enemies ahead of it and kill them, then reload checkpoint. Do this until you have it. But remember, this achievement is extremely easy, especially if you wait until the end of the game where your sword is overpowered.