WWTP => Sadness imagery - 'broken-hearted' showing love is complicated as he is devastated with the relationship ending and the suffering he now must go through.
Porphyria's lover => pathetic fallacy - 'rain' 'sullen winds' 'storm' reflects how love is complicated as the weather conveys the persona's depressing mood without Porphyria
WWTP and Porphyria's lover have similar language which both display the sadness in their relationship