The problem with this series is that the author tried to pull an "if everyone is overpowered, no one is", but then hit the power ceiling so hard he can neither dial it back nor have anyone outdo it.
How in the world are you supposed to beat someone with essentially god mode he can turn on by standing on sunlight, but can also produce sunlight himself? How about the witch with LITERAL INFINITE MAGIC? Or the walking nuke that's also Wobuffet and can just throw anything back at you?