The two of them enter a giant beam struggle (a series staple), but Gohan has a injured arm. Thanks to his will and support from his friends, Gohan overcomes his limits and kills Cell.
Michael B. Jordan is referencing a pretty specific Dragon Ball Z moment and I’ll break it down as best I can.
That idea of never giving up is pretty relatable and one can see how that would apply to a boxing movie.
Goku’s son, Gohan, is fighting Cell, a powerful android hell-bent on the destroying the Earth.