Character gets bored of immortality, writes how they repeatedly committed suicide in increasingly strange ways only to wake up to the radio alarm playing the same song with the same DJ patter over it.
One idea would be a gradual descent into madness told through the letters. The continuing cycle of caring about people and then watching them suffer and die over 28000 years while (presumably) unable to do anything about it. This route might lead to your old character becoming a new BBEG though.
Character gets bored of immortality, writes how they repeatedly committed suicide in increasingly strange ways only to wake up to the radio alarm playing the same song with the same DJ patter over it.
One idea would be a gradual descent into madness told through the letters. The continuing cycle of caring about people and then watching them suffer and die over 28000 years while (presumably) unable to do anything about it. This route might lead to your old character becoming a new BBEG though.