Spike somebody’s guns
Definition 1 of 1
Pro Tip 1/3Idiomatic Usage
Used to describe action taken to prevent someone from succeeding, often in a clever or unexpected way. 
When she presented the data first, she spiked his guns on the proposal.
Pro Tip 2/3Metaphoric Origin
Originally a military term for disabling enemy cannons by blocking them, now applied metaphorically to strategies or arguments. 
By leaking the project flaws, the whistleblower spiked the company's guns.
Pro Tip 3/3Neutral Tone
The phrase isn't inherently negative or positive; it depends on the context it's used in. 
The lawyer spiked the opposing witness's guns with a surprise alibi.