Easiest achievement to earn in the game, IMO. It can be done on any difficulty with any character.
On the menu screen, chose "Single Player."
A list of options come up, which are the following.
The one that we want to do is Score Attack, so chose that option.
The next menu shows three options.
I chose Route A and the game loaded up the character select screen. I chose Jacky Bryant. Once it showed the loading screen with details of my first opponent and the stage that fight takes place in, the achievement is unlocked automatically.
Have fun and good luck! If you submit a negative vote, please comment on my solution as to why you felt that way and I'll happily amend my solution to correct any mistake I made. Thank you!