Suggested by Sonic Harpnote may not be known as one of the strongest Megaman fighters out there but she can hold her own when the going gets tough. Darkside has various energy attacks up his sleeve but the guy isn’t very fast. Harpnote should be able to easily dodge all of his attacks and pelt him with the Harpnote blasts. Ultimately this will chip away at his health until he goes down. With no way to reliably counterattack, Darkside can onlyh delay the inevitable. Harpnote wins.
Suggested by Destroyer The BioLizard is a powerful beast that was even able to go up against Sonic and Shadow. His sheer firepower is way beyond anything that Darkside can hope to dish out. The sheer amount of lasers would also be impossible to dodge. Then The BioLizard also has his portable barriers to protect him as well. Mix all of that together and this is a very deadly battle for the Heartless. The BioLizard wins.
Suggested by Sonic Darkman is a fairly obscure navi. He’s certainly never gotten into the big leagues despite having a hype design and fairly impressive abilities. He’s not someone who will go down very easily and Darkside doesn’t have enough ability to defeat him. Darkside has a good amount of power but he’s just too slow. Darkman would quickly take him down with a barrage of lasers and then that will be the end. There just isn’t a way to come back from that. Darkman wins.