I will admit this selection is probably not an obvious one. This scene from Superman III is near the middle of the movie, and is not especially set up well for a Monomyth interpretation by other story elements. I think it is easier to understand, however, from the ideas explored in the previous movies.
The original challenge and temptation was the love of Lois Lane. In both her discovery of his identity and his decision to become mortal as she, it was a Refusal of the Call of sorts. Although his return to the Fortress of Solitude (see Superman & the At-One-Ment With the Father) led to atonement with Jor-El, Kal-El was not fully reconciled with his dual roles as Superman and Clark Kent. Having failed the original challenge, another Ordeal was required.
The junk yard fight had a physical element: a human-synthesized kryptonite did not weaken him in the same way as the true fragments of his home world. Instead, it left him vulnerable to mortal vice. Perhaps this is one element why Superman has been compared to Christ: Kal-El had not fully experienced mortality until briefly succumbing to its fallibilities and shortcomings. And it is not Superman who triumphs, but Clark Kent, who subsumes him; and then the Transformation is complete, as Kal-El is fully ready to be champion of the people of Earth.