If you have a fight stick with a turbo option. Just set your 'A' button to B (not the B button but the move type) in the control options.
Go to quick play. Choose Mitsurugi. Find a D level opponent. Tape your 'A' button down. Mitsurugi will slash down and then back up. Over and over and beats the AI pretty easily. When the current match is over it will auto select Rematch. Not sure how long it took but I did it for 2 nights starting at level 1. At level 99 I had won about 1000 fights on Mitsurugi. Probably didnt take that long though.
If you do it over 2 nights. One night find a male opponent and the next find a female opponent to get those achievements along the way.
Need help with an online achievement? If I got the game Ill help. Just PM me.
COMPLETED: 108 - RETAIL: 62 - ARCADE: 21 - WP7: 15 - W8: 8 - OTHER: 2
Last Completed: Fighting Vipers(XBLA)