This boss is stationary for the whole fight, however he is large enough that he is always able to hit any part of the arena with either his fists or his flames.
Different attacks he has are Swiping and Smashing with his arms, and using his fire breath to scan the arena with flames.
In order to attack the big guy you must wait for his arms to be on the ground, or as a ranged character just hit him and dodge attacks.
The arms would easily be a Begin Overlap cast to the Player Character to do damage whenever the player comes into contact. Add some 'Move Component To's and you've got some swiping and crushing arms. The flame I would be replicating with a Laser that comes out of his mouth.
It'll be a big Laser, it's gonna be huge. You've never seen the likes of this Laser before.
This sketch of the boss battle I have in mind, The Giant Evil Rainbow Monkey, shows a quick visual. He will be big, He will actually have arms, He will be in front of a large rainbow.
The player platform will be a large solid cloud.
His attacks will consist of his Giant Laser, Giant Hands, and the ability to summon Skull Heads.
The laser will move at a medium pace across the platform in a zigzag pattern that the player will be able to dodge. This will be done by rotating the head.
His hands will have two primary actions, possibly a third. Smashing down, Swiping across, and Punching from below.
His battle will change at 30% health by making him Enraged. This means I will have him do a short animation of bursting his veins which are filled with rainbow blood and speeding up the duration of each Move Component To.

