I cannot find a clear answer on the difference of these (怖 & 恐) two kanji. They both read (oso)reru & (kowa)i - And they both seem to mean the same thing... Which is: 'dreadful; frightening' and 'fear, be afraid' respectively.
Perhaps a kanji master can explain this? I mean, is it more than them respectively being an adjective and a verb?