You might have a look at C.S. Friedman's "Cold Fire" trilogy. Several of the main characters are quite powerful sorcerers right out of the gate.
https://www.goodreads.com/book/show/...ack_Sun_Rising
"Tigana" by Guy Gavriel Kay also has some fairly powerful POV sorcerer characters, although the MAIN main character isn't a wizard at all.
https://www.goodreads.com/book/show/104089.Tigana