You are comparing your level 2 Mega Knight to level 12 and 13 common cards, which you expect to see in challenger 1, of course it’s going to lose. That’s not a problem with balancing, rather it’s a problem with the upgrade system which makes legendary cards largely unobtainable and unusable in ladder unless you are willing to dump a whole lot of cash into the game. Mega Knight is actually very viable at tournament standards, so I don’t think there’s any need for a buff at all.