What was Saint Justin's miracle?

Answer 1

Saint Justin the Martyr was declared a saint long before the canonization process was put into place and no miracles were required. He died as a martyr and that was all that was required of the early Christians for sainthood.

Answer 2

Saint Justin Martyr is not traditionally associated with performing miracles. He is more well-known for his writings defending Christianity and his martyrdom for his faith.