When thinking of antonyms for the term "most split-second," words like slow, gradual, and deliberate come to mind. These words refer to actions that are intentional, considered, and done with a greater amount of time and care. Slow actions involve taking one's time to think and execute something, rather than reacting impulsively. Gradual actions happen over an extended period, rather than in one split second. Deliberate actions are done intentionally and purposefully, rather than instinctually or reflexively. By understanding these antonyms, we can see that the phrase "most split-second" refers to actions or decisions that are quick, sudden, and reflexive.