The word surprise has many antonyms depending on the context. For example, in a situation where you want to avoid surprising someone, the antonyms would be expected, predicted, anticipated or foreseen. In a situation where the surprise is a negative experience, the antonyms would be relief or reassurance. Conversely, in a situation where you want to amplify the element of surprise, antonyms such as predictable, boring, dull or mundane would apply. In summary, the right antonym for surprise depends on the context, tone and desired outcome of the situation at hand.