This page of the guide to Dragon Ball Z: Kakarot has a walkthrough for the following missions: King of the Demon Realm, Echoes of Evil.
DBZ Kakarot - King of the Demon Realm
You play as Gohan who is about to face the King of the Demon Realm - Dabura (level 64). Your opponent is quite strong, likes to fight in close combat and performs strong combos. In addition, the enemy has fairly fast Ki attacks that are difficult to avoid at a short range. Focus on blocking, stun attacks and end your combos with a strong Ki technique, such as Super Kamehameha.
DBZ Kakarot - Echoes of Evil
Babidi took control of Vegeta. Goku must fight Majin Vegeta (level 66) - this enemy can be quite problematic. Your opponent is really strong, uses all of Vegeta's techniques, and is dangerous both at the short and long distance. As always, dodge, block and then counterattack. If necessary, use healing items.