Loot Hero DX

After beating the game simply replay the first level and your character should be overpowered enough to finish the level in under 15 seconds, I recommend upgrading your speed skill to level 9 for this.

I show this Achievement on level 5 in my Achievement Walkthrough starting at 4:09 minutes into the video.

Before beating the final level (Volcano) go back and replay the first level (The Woods) and you should be both fast and strong enough to just hold right and wipe through the enemies. If not, just rank up your upgrades then repeat