This will unlock at level 80. You shouldn't need to grind for it if you plan on doing the other achievements. For reference, as of this writing, I am at level 82 and haven't finished adventure mode yet. So this will likely come naturally as you unlock the other achievements.
Glitch warning: when you go from level 79 to 80, do not skip the stats and animation screen. Let it play out fully and then wait a moment before doing or clicking anything. If you skip too fast, the achievement will not unlock. If this happens to you, you can level up once more and wait as mentioned, and the achievement will pop.