The phrase "breakneck speed" means doing something very fast or quickly, often without giving much thought to the potential dangers or consequences. Full definition
Soaring through the skies as Pit may seem serene, but Nintendo is throwing combat chaos at breakneck speeds at Pit from beginning to end. (gamedynamo.com)
Driving on walls, inside cylindrical tunnels, destroying bridges and obstacles, and barrel rolling off massive jumps at breakneck speeds of 400 - 700 km / h is incredibly satisfying. (deathbybeta.com)
Snowpiercer alternates between sudden violence, high camp, and heavy - handed political allegory with breakneck speed, and even when its disjoined plot mechanics seem a little too convenient, it's brimming with new cinematic technique. (scene-stealers.com)