How do you beat the very last boss in starfy

If you mean the very, very, VERY last boss, You first have to dodge him when he zooms in on you. then star spin him and run. repeat this up until he goes to the center. then just doge his attacks. after that attack, he'll zoom at you again. Star spin him like before but don't worry about running. After he has been lowered to two health, He'll zoom at you again but he'll sort of chase you. Once he goes off screen, he'll come back and try grabbing you again. Before he reaches the otherside, he'll get tired. Now is where you hit him the final two times and you will be done.