as a psychologist, and a student of stalin's insanity, i can guarantee that no one could cure the guy. he was a sociopath, and not so brilliant. he was definitely crazy and also extremely evil. just because someone is crazy doesn't mean he isn't evil. (think of hitler, charles manson, etc.)
there is no cure for sociopathy. i would vote for a lethal injection for stalin, if i was his shrink.
even if his dementia started in 1924, his sociopathy started long before then.