“Guardians of the Galaxy Vol. 2,” Rated PG-13, 137 minutes 2 1/2 stars With its audacious—visual style and crackling humor, “Guardians of the Galaxy” creatively reinvigorated Marvel Studios’ comics-to-movies franchise in 2014 and introduced a charming new set of heroes to a universe that sorely needed them. The James Gunn-directed film, which also provided a breakout role for Chris Pratt, was one of the highest grossing entries in—Marvel’s vast catalog, making a sequel a certainty. “Guardians of the Galaxy Vol.