So in Iron Fist #7, Iron Fist fights a mind-controlled Shang-Chi. Interestingly, Iron Fist says that Shang-Chi is probably the only person on the planet who can beat him in a martial arts fight. At first Shang-Chi is winning but Iron Fist is holding back and Danny decides he can't hold back if he's going to survive. Then the battle becomes basically even. After the fight ends when Iron Fist ko's the mind controller, Shang-Chi, who has come to his senses and is not one for bragging, states that he fared the better of the two in the fight. The issue comes pretty close to saying Shang-Chi is the more skilled of the two.
In Superman #30, Sinestro fights a Superman possessed by Parallax. He lures Superman/Parallax into a trap where Qward warriors knock him out by throwing their thunderbolts at him. This is a pretty poor showing for either Superman or Parallax, much less the two of them combined. Then, when Parallax leaves Superman's body, Sinestro singlehandedly fights Parallax for hours. I didn't read the previous issue so don't have the full context, but if there were no contingencies, Parallax now looks herald level.
They fought once in the '70s (a fight that was partly staged), and never again since, until now.
It's quite significant in terms of Shang-Chi's rep, because there's been a growing school of thought that Danny has gotten better than Shang in recent decades, due to the fact that he's continued to get pushed against mainstream Marvel characters (fighting many more superhumans, for example), whereas Shang's solo titles have tended to operate in their own little world, and Shang has appeared much less frequently in recent decades, clocking up fewer good showings as a result. Contrary to the above school of thought, I always expected that if they fought again now, they'd still be portrayed as equals/peers (as they were in the '70s), and this seems to confirm that.
Now, when oh when will we finally see Shang throw down with Daredevil...? That's one Marvel MA match-up that's LONG overdue.