Before tackling a boss in Dragon Ball Z: Kakarot you need to ensure that you are fully charged as you will need to have as much Ki as possible if you hope to defeat them. Although charging up your Ki is time-consuming during a fast paced battle it is also the best thing you can do when there is a safe distance between you and the enemy.
Collect Z Orbs
It is important that you collect the six different types of Z Orbs whenever you come across them as they allow your character to attain new abilities through the 'Character' menu. The colour of the Z Orbs denotes the different locales you can find them in. Green means forest, blue means underwater, and red means desert. Timed events that will spawn more Z Orbs are triggered when you find a Z Rainbow Orb.
Complete Side Quests
The side quests in Dragon Ball Z: Kakarot are wothwhile doing as they are able to net passive bonuses and acquire useful items for your journey. These include consumables, ingredients for food, and giftable items that will help you level up your communities. You will be able to find side quests on the map by looking for a bule exclamation mark.
Defeating Bosses
The bosses in Dragon Ball Z: Kakarot have plenty of health and use carefully timed attacks and patterns which you will need to observe and study in order to know when to counter attack with your high-damage Super Attack to defeat them. This will typically be when they are winding down an attack or if they have run out of Ki after a barrage.
Equip Health Items
The bosses in Dragon Ball Z: Kakarot have plenty of health and if you get involved in a drawn-out battle with one you could end up with very little health. Make sure before you confront them you delve into the menus and equip health restoratives to your bar so you can use them in the upcoming battle. If you don't have any health restoratition items you may want to consider exploring the local settlements for an item vendor where you will be able to pick some up.
Super Attack Assists
During certain points of the story in Dragon Ball Z: Kakarot you will will be able to call upon other characters to assist you in battle. Make sure that you choose a partner that has a Super Attack that is able to do optimal damage when you do a combo together.