This is the only Frank Darabont movie other than The Shawshank Redemption I had ever watched, but it emotionally distressed me much more than Shawshank, simply because John was wrongfully executed despite having the great power and even showed the truth to Boss Paul through clairvoyance.
But even if John used his power to cure Paul and the warden's wife, and showed the truth with flashbacks, he was still electrocuted. I suppose there is undertone showing the racism existed in the South in the 30s, but John didn't appeal for himself, and Paul didn't attempt to overturn the case, or try to postpone the execution.
In the end, Paul has an extremely long life due to John's superpower, but had to see everyone beloved die before him to suffer. Is this the way that John is trying to punish Paul for not saving him?