AlexGI think you’re asking about the classic two-edged sword of transformation.
One – of absolute power, corrupting absolutely.
And two – Stan Lee’s statement of with great power comes even greater responsibly.
Psychologically, it all depends upon the individual whose the recipient of the blessing (or curse) of the transformational change. Some will certainly rise to the occasion and become better individuals, others, perhaps just as good to start out with because of their inherent flaws will be enamored (even possessed) by the more hedonistic / narcissistic elements of their change and become far worse in nature. This is far more likely if the character is “pre-arranged” for such a fall from grace. Nor is it to say that from time to time some of them might not try to redeem themselves, but more often then not it’s not something that you see occurring with much frequency in these types of stories.
“I like a good story well told. That is the reason I am sometimes forced to tell them myself.”
~ Mark Twain / Samuel Clemens (1907)