I just finished all the missions and #19 took me four and a half hours in my last session before I finally got it. So I'll share my methods for what it's worth.
Mission #17 - I chose Zangief like many other folks and gave him gems that boosted damage for hitting a certain number of special moves and recover health after being hit by the opponent's special moves. Hugo was a bit of a problem, as you can't get him into the Powerbomb repeat or Lariat spam either. You have to exercise a little patience and use the Lariat or Powerbomb when he whiffs or you block an unsafe move. Same for Marduk. I was able to get Zangief in the Powerbomb loop fairly easily.
Mission #19 - I chose Bryan and Zangief in that order. As soon as the match against Ogre starts, tag in Zangief and use the Powerbomb loop on him. He's really no trouble. Now when the match against Akuma begins, Akuma will through a fireball 95% of the time. So activate Bryan's Super Art immediately for some good damage right away. Then use Bryan's Flying Knee special move repeatedly, as it goes through Akuma's fireballs. Be patient, and try to punish Akuma when he throws a fireball, jump back when he uses his Super Art and punish with Flying Knee. It may take awhile to get the spacing right for the move. After Akuma uses his heal gem, you should have built up enough meter to use another of Bryan's Super Art. Like I said earlier, I spent four and a half hours on this but I beat Akuma within 20 minutes of putting Bryan first and Zangief second. I came very close a number of times trying to Lariat Akuma to death, but I found Bryan to work better for me.
Last edited by Midersaw; 03-22-2013 at 02:48 PM.