This mission requires you to block 50 consecutive attacks. If you miss one, you have to start over from zero. As you can imagine, this is quite tough. Thanks to a non-obvious fault of the game, there's a really easy (but kind of long) way to complete this task. As soon as the match starts, and you can control your character, press the Block button (R2). If done correctly, your character will get into a defensive position and won't be able to move. The computer controlled opponent should start to punch and kick you (if you're lucky, he'll hit you with a weapon). As long as you hold down the Block button, you won't take any damage and you'll start earning your 50 blocks. As soon as you see your opponent do a move that looks like it's unblockable, quickly pause the game. Check your Block counter at the bottom of the screen to make sure it's not at zero, then quit the match. The game will autosave your progess as it takes you back to the menu. Once
you're back at the menu, press X two times to go back into another match. As before, hold down the Block button when you have control of your character, and quickly exit to the menu as soon as you see your opponent do a move that might drop your Block counter down to zero. If your counter accidentally drops down to zero, reboot your PS2 immediately (don't exit to the menu, or let the game end the match, or else it will autosave your zero count). The game will reboot and pull your last saved progress off your memory card. If you keep this up, you'll eventually get to 50 Blocks. This secret trick was successfully tested with the AI Difficulty set to Low. I don't know how well it'll work on Medium and High.