The warrior characters of the Dragon Ball Z franchise are all about testing yourself and pushing yourself beyond your current limits. You can do the same in Dragon Ball Z: Kakarot as you battle some of the fiercest enemies the series has ever seen. If you get a little out of your way, you can replay many of the more difficult boss battles the game has to offer, but there is a certain way to do it.
After the Frieza Saga and your return to Earth, you have the option of using the Dragon Radar to locate the seven Dragon Balls in the game. These Dragon Balls are small stones which, when put together, summon a mighty dragon that will grant you nothing. any wish. One of those wishes is to give you the chance to resurrect them to try again. These battles are a great way to gain experience if you want to train any of your characters in the game.
First you need to find the Dragon Balls. There is no defined location for them. They are scattered all over your world in the game, and you must find them using your map. It's hard to miss them because you can see them as little orange orbs on your map. Look around the area to find them. You can see how many you've collected in the upper left corner of your screen.
When you have all seven dragon balls, go to your main menu screen and summon Shenron. You should have the option of resurrecting any bosses you've defeated to try and fight them again. These are fierce battles, so make sure you're ready for a fight. You can do this as many times as you want to train your characters, but Dragon Balls have a 20 minute cooldown, and that's the time to play. So you may have to wade through the game, complete other side missions before doing them again.