A lot easier than I thought it was going to be.
VS match against a Noob CPU and pick Jago. All I did was get the CPU into the corner and repeated the same simple combo. Wind kick (or any opener) then straight into the Endokuken ender where he throws a fireball and launches the opponent up into the air. Each one of those could be a juggle a hit. When you build up your shadow meter, and after your ender, do a Shadow Wind Kick for 5 juggle hits. You will definitely build up your shadow meter more than 8 times in the match, so you have lots of opportunities.
If you pull off the ultra at the end of the match you'll get at least 10 more hits + the Shadow Wind Kick on the opponents' way down and you should have no problem getting this. I didn't even get my Ultra off and was still able to unlock the challenge.