In the end of the world 4 you will face the most difficult enemy so far of Mario + Rabbids Kingdom Battle. Before confronting this final boss, visit the base to assign your last orbs of power and equip yourself with the best possible weapons, Mario’s arch enemy is waiting for you. Select a character who has the ability to heal, such as Princess Peach.
Bowser will appear protected by 4 Valkyries, you have to defeat them first of all, use area attacks as explosive to damage several enemies at once. Do not attack Bowser until you defeat all Valkyries. When we do enough Bowser damage we will move on to the next round.
In the second phase make sure that lava rains do not hurt us is key. In this round, we will have to go first of all to the enemies. The Bowser machine gun will not appear at this stage.
If we can move to the third stage without having eliminated all the enemies, they will join the new ones. Kill first of all the henchmen who help the final boss.
In the last round, if there are not many enemies you can focus on attacking Bowser, three rounds should be eliminated, but you can play it to lose all progress. To stun Bowser and leave him exposed to the attacks you must wait for him to use his shell attack and when he hits a black square he will be stunned for a round and will not be able to protect himself from the attacks.
Use your weapons with more damage to destroy the final boss and you have managed to complete Mario + Rabbids Kingdom Battle. He is the most complicated boss of the game, cover yourself well and finish first with the minions to focus on him.