First of all, change the battle settings (Help and Options > Settings > Battle Settings) to:
CPU-Level: 1
Play time: Infinite
Round Set: 3
Defense Level 1P: 8
Power Gauge 1P: MAX
Now go to story mode, pick B.Jenet and check who's gonna be your opponent. You want to fight against Kim Dong Hwan. If you end up with someone else, just quit and try again.
You may want to map the buttons to make this easier. You need to hit LP, LK and SP to perform the move (X - A - Y in default config), it has to be on sequence, but very fast. Change the B button to "Strong Punch".
Now to perform the move you should hit X - A - B instead of X - A - Y.
Once the fight starts go all the way to the left corner. Now wait until Dong performs his "Thunder Slice"
which is very easy to defend (he will usually hit you low with a kick and then perform it).
Once you "Just Defend" his move (when you just defend a blue shield appears towards your character and also a message on the screen) press your mapped buttons in order: LP - LK - SP (X - A - B if you mapped as I said).
The move should come out and the achievement will pop up.
Note: You can map the buttons as you want. Change to one that suits you best, just remember the order you have to press the buttons: LP - LK -SP. I personally used this configuration with my index finger on B, middle finger o A and ring finger on X.
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