I'm not gonna pick and choose here, but I'd like to make points
-Almost certain Heihachi actually CAN understand english. In Tekken, every character (for the most part) speaks their native language, and they all seem to understand each other.
-Evil Cole now has the power of the beast, but it can't be easy for him to hold up, seeing as how he's never really gone full beast. He has some basic hand-to-hand knowledge and has his amp with him. He has very destructive powers, can summon spikers, and can trap his enemies. A lot of Evil Cole's more destructive attacks really drain him, and can leave him in a really bad position depending on the environment. Evil Cole can climb as well as fly, to a degree, giving him a definite terrain advantage.
-Heihachi has expert hand-to-hand knowledge. He doesn't quite have a "Beast" form as Evil Cole does, as he is the only playable Mishima that either doesn't have or never uses the Devil Gene. If you want to count Kuma as a part of this fight due to his inclusion as a Super in PSAS, then you add another strong fighter to Heihachi's side. Also, Heihachi does have limited electric attacks in the form of his Electric Wind God Fists. He is the King of Iron Fists, and has beaten about 60-70 of the world's best martial artists, animals, and beasts alike. Also, he has been thrown into a volcano at least once. That should be mentioned.
Cole has a range and terrain advantage, and can hit Heihachi from a distance. Heihachi hits like a semi-truck and possibly has a bear that knows Karate with him. Heihachi isn't affected too much from the ranged disadvantage, however, as he is pretty fast via wavedashing, and through canon. Cole can definitely get away from him if there are walls to climb. Both can take a pretty huge beating.
It could go to either, really.
Fresh to death