Quan Chi is a more advance character that requires a lot of mind games and prediction.
Use the correct groundburst at the right time, dont ever mess up zoning with him, especially with trance, its not a fullscreen move
Quan chi has a lot of resets and mixups, dont be too concerned with the low damage on some of his bnb combos.
Mesmerize is his most important special move, don't ever get wise with saving meter for a big x ray combo, his x ray is a last resort tool, regardless of its armor and damage.
Keep your opponents meter down, provoke projectile spam or wake up by building distance and hope for a trade of with trance or mesmerize. If you get hit by your opponents projectile at the same time you trance them, they will be possessed, leaving time for you to use super skeletal buff to increase damage and the health you just lost, land a follow up with a trance link, it will work as if they weren't hit by it the first time.
Example, credit to FROG55JQN
I have much more Quan Chi strategies to show off in a guide I'm currently working on.
I'm Glad to help out.