@@Werten25 I can see the problems in putting him on Rainbow Cruise. Bowser is a big heavy character not suited for jumping. I think the Multi Man Melee with the Marios is fought there. They are better equipped for it.
You can cheese the Giant Link fight by standing on the floating rock at the beginning of the fight. He will try to attack you, but fall to his death. Dr. Mario is pretty annoying because of all the bricks and surface is pretty slippery on that stage. If you lure him to the edges though, sometimes you can get him to kill himself. Luigi can also be pretty annoying since Mushroom Kingdom II is small stage, but he tends to kill himself lol. Bowser can take a lot of damage, but he's also a big target and not too bad.