This is the 1st mission's achivement in Story mode, it'll unlock once you beat the boss,
It can be done on any difficulty.
He's got a charge attack and a projectile, when he charges you can jump out of his lane, then go in for hits once he stuns himself running into the wall.
The projectile is also easily dodgeable, lots of lead time. Once you shave off enough health he'll flash red and attacks will speed up.
If you finish him off with your Super, you can also earn the following: