Final answer:
In this sentence, 'GREATLY DISLIKED' means 'abhorred' or strongly disliked.
Step-by-step explanation:
In this sentence, 'GREATLY DISLIKED' means 'abhorred' or strongly disliked. The word 'greatly' emphasizes the intensity of Louis's dislike for Brussels sprouts. This means that he had a strong negative feeling towards Brussels sprouts.