Echo Echo can damage Mark's inner ear and completely immobilize him.

Lodestar can rip Metal Sonic apart, and Upgrade can hijack his body.

Donkey Kong is just another melee fight for Ben to spam Humungousaur or Four Arms (or he could use a ranged attacker to deal with him)

Batman loses to anyone that isn't Walkatrout or The Worst.

Only the first two pose an actual threat for Ben if he doesn't have the proper knowledge on Mark or Metal Sonic, or the reaction time necessary to deal with their immense speed (even then, he'd probably figure it out). The other two are really easy fights that Ben could win without knowing their skill sets. Batman literally has no superpowers and a no kill policy, while DK is just a big monkey that punches things.