Lucky for you, I grind a
LOT on the Spirit Board and love finding exploits for the AI. And I just so happen to have an Omega Ridley video that I posted to Youtube. He's one of the more brain-dead stupid ones once you find the hole in his AI.
I know this looks stupid, but trust me, it works well more than 2/3rds of the time. I've got quite a few other videos on my channel for some of the harder Spirit Battles. For most of the Legendaries, Ganondorf is able to massacre them pretty badly. He's heavy, has 2 very powerful command grabs, massive smash attacks, and a super armored kill move (grounded Warlock Punch). The only thing bad about Ganondorf is how easy he is to gimp, especially against nimble tag teams like Pyra, Mythra, Ceada, Mecha-Fiora, Black Shadow, etc. Once you're in disadvantage and offstage you're ****ed.
Black Hole + Giant is a pretty broken combo on Ganondorf that is able to kill most opponents with one or two Doryahs if you put some charge on the second one. Another broken combo is a Giant + Screw Attack + Lightweight style dojo with Samus. Against one opponent (or a team that's all out at the beginning), double jump + Up B carries them all the way up to the blast zone.
In general, the Super Armor ability breaks the game. I actually avoid using it because it makes so many of the challenges just not fun.