What math subject comes after Complex Analysis for physics and electrical engineering majors?
With Complex Analysis you have reached the end of the sequence of undergraduate analysis courses:
Calculus I -> Calculus II -> Calculus III -> Differential Equations -> Partial Differential Equations -> Real Analysis -> Complex Analysis
There is no math class with Complex Analysis as a prerequisite.
Parallel to the analysis track physics and engineering majors should take these math courses:
Advanced Probability and Statistics
For theoretical physicists, courses in Differential Geometry and Topology will also be useful.