This is a tribute to DBZ Battle of Gods! Goku is definitely a strong character, but the movie didn’t do him justice. Goku’s power far exceeds that of most characters, but can he take on Grimmjow? Grimmjow has super speed which he could use to give Goku a solid fight. One would think that Goku could take a win, but we can’t count Grimmjow out. Grimmjow wins.
Update 8 7 2020 Grimmjow has lost his high above status and no longer has the power to defeat Goku. Goku wins.