Ok, here's what you do...atleast for me it worked.

Pick Captain Marvel and stay as far away from DK as possible. Everytime he tries to come towards you and attack, do Captain Marvels lighting move, then quickly evade using his teleport..

If you are good with the Captain, evade with teleport and try to combo him, make sure DK has no breakers, if he does, its almost a garranteed 30 to 45 percent combo.

Or if you decide to go the cheap way and find him way too difficult to beat... use Superman or Flash's infinite---> since its offline I would recommend doing it, hope you have more success doing Superman's ground pound and pro ground pound moves. I could really never do his ground pound then pro move for more than 2 consecutive times.

Superman's ground pound pro-move. The CPU always falls for it. That's how I beat the game on very hard without continuing.

I just fought him. I've played the game to the point where he's not hard on 3 round wins either. I got that Arcade Champion trophy (i think thats what its called) where you beat the game on the hardest difficulty without continues. I set it to the best of 5 wins too! Lol, I also play it a hell of alot online so DK is a bitch compared to people online. I just brought out Superman and pulled my biggest combo i could out on him.

you dont even need a strategy. He was really easy to me when i fought him. just play with who you're best with.