@rlier23 it's pretty brutal lol, the game is pretty easy until you beat it and then it gets pretty difficult. then when you beat it again, the coliseum is even harder xD
what i did was get a bunch of boosts from the hat shop's upgraded sleep cap, used the heals that give you an extra life bar you can get at the shop at the top right, and then used the upgraded meta knight mask to take on the coliseum. as long as you have over default health, you can still shoot sword beams so with that extra HP bar you have a lot more leeway to shoot beams. you also get a little bit of health back when you attack with it.