I understand that the answer to this question must vary from person to person. But this is just my point of view.

There are a couple of characters whom I’d like back from the dead as they would shape Harry and the whole trio’s fate differently. But if I had to choose one, then it would be Sirius Black. Not only he was a fellow Gryffindor, but also Harry’s godfather. His death affected Harry so much that he was compelled to use a curse on Bellatrix out of hatred. He not only would have protected Harry during the Battle of Hogwarts but also shaped his character further in life guiding him through life.

His presence made so much sense as Harry looked up to him as a father figure as Sirius was his only literal family. Sirius always made bold choices in life and was distinct from the other members of the Black family. He was a true Gryffindor and fought till his last breath as Harry’s fate depended on it to an extent.