Available after doing the Porunga Part 2 sub story in the end game of Dragon Ball Z: Kakarot, the return to Earth is very eventful. This sub story is one of a series of 3, allowing you to face Frieza, the evil emperor, again.
The Return of the Emperor
After passing the trial of wisdom, Goku was able to fulfill three of his wishes and one of them was Freezer's resurrection. Near the West City lighthouse, just outside the city, go and pay a little visit to the emperor who seems to be in pretty good shape for a dead man. After a few seconds of astonishment, Goku will propose a little training fight to Frieza in his first form, the one closest to his father.
Once the fight ends, Frieza and his oversize ego won't stop there. This one will go straight to its final form after a short dialogue. You don't get your health back between the two fights, so make sure you have at least one healing item. Its final form is the same as the battle during the main adventure.
You can acquire Frieza soul emblem once you have won the fight.