@swimminginsand: I don't think Karma was weak before she absorbed the Devil. She must have been quite strong to begin with or else why would the Devil come in contact with her in the first place (and the devil simply let a large dragon swallow it, without any fight, doesn't that seem odd).
Also if just absorbing a Devil gave her cosmic level power, then any other being could have achieved the same result as well.
So, i would say that, Karma probabaly had been of equal strength as that Devil (who was already top class in strength), and merging with that Devil gave her cosmic level strength.
As for the Elf Onee-san, she never really fought Karma seriously (neither did Karma did as well).
Also if just absorbing a Devil gave her cosmic level power, then any other being could have achieved the same result as well.
So, i would say that, Karma probabaly had been of equal strength as that Devil (who was already top class in strength), and merging with that Devil gave her cosmic level strength.
As for the Elf Onee-san, she never really fought Karma seriously (neither did Karma did as well).