Final answer:
The subject of this question is English. The phrase 'a last great wave of regret-ful memory' describes the intense feeling of sadness and longing in the given context. It is an example of emotional and descriptive language used in literature.
Step-by-step explanation:
The subject of this question is English as it is asking for the definition of a particular phrase in the given context.
The phrase 'a last great wave of regret-ful memory' refers to the intense feeling of sadness and longing that Leigh-Anne and Joe experience as they say their final goodbyes.
This is an example of emotional and descriptive language commonly used in literature to evoke strong emotions in readers.