Slightly soporific ending can be described as a dull and lackluster conclusion to any story or presentation. Some synonyms for this phrase could include a sluggish, lethargic, or uninspiring ending. Other words that could be used to describe this type of ending include a slow fade out, a lack of climax, or an anticlimactic finish. Some phrases that could be used to describe slightly soporific endings include a gradual decline, a fizzling out, or a weak finish. When looking to avoid a slightly soporific ending, it is important to focus on creating a strong and engaging conclusion that leaves your audience feeling satisfied and fulfilled.