This seems rather self explanatory, but I feel it is poorly worded;
I ran through part of the game as Vhaidra, the monk who fights with her fists/feet. After playing through a ways, I created Dorn, the Barbarian, and barely part way through the starting location popped this achievement.
Because of my experience, I believe that 1000 melee kills period should unlock this. I would however welcome any and all input from the community.
Happy hunting (>*_*)>