Mighty No. 9

This achievement is tricky to set up. I ended up getting this naturally by winning with 0 lives left. The head boss is hard until you know how to beat her.

To set this up you will play through the Battle Colosseum until you get to the head boss. Once you are there let her kill you until you have zero lives left. Doing this on normal will ensure you have an energy tank or two. Once you have zero lives go on and beat the boss.

The game considers “low health” when Beck is slouched and tired. Once you have the boss on the second stage and low on health herself let her hit you until Beck is slouching (if you don't end up that way naturally that is).