1. The Task Master
2. Nightwing
3. Winter Soldier
4. Deathstroke
5. Batman
6. Gamora
7. Wolverine
Fight takes place in the octogon, on a planet under a Red Sun. How far does he get relying only on his hand to hand skills. No powers or gadgets. That includes Wolverine's healing factor and Batman's utility belt.
He's skilled in Kryptonian martial arts and has recieved fight training from Batman and Mongul. I bet he could make it to Deathstroke at the very least. Batman would take him to school though. I don't think that Taskmaster would be much of a challenge. Being able to mimic a fighting style doesn't mean that it wont hurt him when fighting against it.
And....? It doesn't matter who's fighting style he's memorized, if they can be hit then he can be hit. Superman is definitely not a small man by human standards. Physically he's bigger than most of the list, Winter Soldier and Wolverine are the only two that out weigh him and Deathstroke is the only one he wouldn't have a height advantage over. My point is that even a powered down Superman would still be able to put a non-super powered being on his/her ass. Having photographic reflexes has no bearing on their ability to take a punch.
The fact that everyone here can take a punch/role with a punch really well, and outskill him significantly, does.
Sure, he can fight and has martial arts training. He's no slouch. Everyone here is a lot beyond no slouch and fight people who are as big or bigger than him, and more skilled, and come out on top.
Weight matters in a fight, but it's a minor factor compared to Taskmaster's range of skills, Nightwing's crazy agility, Winter Soldier's skill and cyborg arm, etc..
Superman might capitalize on his opponents underestimating him w/o powers, thinking it'd be a cakewalk. Not much of a chance for Batman and Nightwing to fall for this as they should be well aware of his H2H training.