Ekko 2XKO combo: 714 damage, medium, by Katsugami. Another version, if Ekko has 0 energy, so it's a version without Ekko's LV1. Be careful with the second…
M > H > 2H > j.9M > j.H > j.S2 > 1S2~[1] > 2S2 > M > 2H > j.9[H] > ~j.S1 > ~j.S2 > 2T > j.[H] > j.S2 > S1 + S2
Another version, if Ekko has 0 energy, so it's a version without Ekko's LV1. Be careful with the second 'S': make sure to keep 1 held down so that Ekko's kick makes him step back.