Suddenly cuts a quiet scene to the opposite mood for a laugh or a shock.
"It'll be fine" followed by a chaotic scene, a boring daily routine followed by an explosive product scene.
Generate the two clips with extremely different color, camera movement, and sound. Cut A's sound completely right before the cut, and start B loud right away. Don't use a fade.
Two-shot sequence: Shot 1, a quiet library at night, a man whispers to a cat on his lap, soft lamp light, near silence, 3 seconds; smash cut with no fade to Shot 2, a roaring stadium crowd under blinding floodlights with loud cheering and a drum, 2 seconds. Sound cuts out completely at the cut.