The alicorns and Pinkie Pie with toon force could possibly beat him. He wins against everyone else besides the mane 6 with elements of harmony and Discord. No way is he beating Discord who is a top tier reality warper. Also the Elements of Harmony are basically a plot device that's pulled out when they face a foe they can't beat so Superman probably gets turned to stone and displayed in Celestia's garden. Also Ponies are relevant to comicvine now since there's a comic series. A pretty good one too.