For "cadence" meaning rhythmic flow or pattern:
* Dissonance: Lack of harmony or agreement.
* Chaos: Complete disorder and confusion.
* Disruption: Something that interrupts or breaks the flow.
* Staccato: Short, abrupt, and disconnected.
For "cadence" meaning the rise and fall of the voice in speech:
* Monotone: Speaking in a single, unchanging tone.
* Flatness: Lack of inflection or expression.
* Dullness: Lack of interest or excitement.
For "cadence" meaning the pace or tempo of something:
* Stasis: A state of inactivity or lack of change.
* Pause: A temporary stop or interruption.
* Slowness: The quality of moving or happening at a slow pace.
Ultimately, the best antonym will depend on the specific context of your usage.