How are the endings effective in: Cousin Kate, The Goblin Market, Jessie Cameron and Maude Claire?
Since enotes allows students to ask only one question at a time, I will address the first poem on your list, "Cousin Kate."
"Cousin Kate" is the story of a poor young woman who is seduced by a "great lord." She is taken to "his palace home," where she leads a "shameful life" as his "plaything and his love."
Later, the lord meets Lady Kate, a woman of his own social standing. He marries Kate, and discards his mistress "like a glove." The mistress is miserable:
So now I moan, an unclean thing, Who might have been a dove.
The ending of the poem is particularly effective because it contains a surprise: the mistress has borne a child to the lord, whereas Lady Kate has not, leaving the lord without an heir.
For all your clothes and wedding-ring I've little doubt you fret. My fair-haired son, my shame, my pride, Cling closer, closer yet: Your father would give lands for one To wear his coronet.
The effectiveness of this last stanza is strengthened by the use of three "shining" images that represent each of the poem's characters: Lady Kate's wedding-ring, the mistress's "fair-haired son," and the lord's coronet, or crown.