re: Was Harry Potter a great or average wizard?

Harry was an above average wizard who tried hard and maxed out his abilities but he was far from a great wizard. While he wasn't book smart he did have the real world experience. He was also way ahead of his peers in battle experience. He took over as the instructor of Defense Against the Dark Arts in the Room of Requirement for Dumbledore's Army when Umbridge took over Hogwarts and banned the practical teaching of the class instead instituting a policy of learning it from a historical perspective.

Thing is, Bellatrix, or any other Death Eater, could have killed him easily but they all passed on the deed so Voldemort could do it himself. That was the fatal flaw in their plan, it wasn't Harry's magic that made him impervious to Voldemort it was his mother's magic and the final spell she cast, protecting him with her life. It was magic Voldemort could not understand so he did not have the power to kill Harry, but Bellatrix could have finished him easily. The protection didn't extend to anyone else, he was only impervious to Voldemort.

Oh, and the most hated character in this entire series is Dolores Umbridge. I loathed her and wanted that B to die a horrible death.