Set Difficulty in options to "Hell" set number of arcade rounds to 5. ( I also set timer to 30 sec but I don't think there's a need).
Go to Arcade mode and select either Shadow Labris or Akihiko as they will fight Kanji first who can throw out some crazy combos.
When the fight started I just did something else keeping an eye on Kani beating me up incase of the trophy popping. It took me 4 rematches but then he did a combo that took away ~70% of my characters health and killed me.
Alternatively boost it with your friends with a 1 hit kill attack.