Shang tsung is my second (after Liu kang). If they are in your face, it's perfect, because u can start comboing his as$. I'm on xbox, so il tell u the xbox controls, and you figure out the button translation to ps3 lol. Sorry cbf doing it myself.
My favourite combo is : back+X, Y, X, B.
But instead of the B at the end, I usually do: back+X, Y, X, then down+up+B straight away. So instead of the last kick, he ends with a fireball from under them, and then you can continue doing combos, or more fireballs from there. You can actually do it with any combo (replacing the last hit with a special move).
There are 3 hit combos that do more damage than the one above, but I like this one because it has a more forgiving timeframe to branch into advanced combos