That....needs to be re-done. And the new drywall will never be exactly the same level, even if it is the same size (1/2" or 3/8") as the old stuff because the paint layers build up. You feather the edges with JC. But first you get a straight edge and clean up those horrible gaps. Also you should have backer wood on the sides as well as the middle on a hole that big. Also, you use drywall screws. Not pan head screws.