Let's go with: sabotage.
We finally got around to building our backyard compost this morning. It'll be nice not to have to walk all the way up to the one by Kat's parents house anymore.
Okay, 'all the way' might be a slight exaggeration. But with the weather getting colder it was about to feel a whole lot farther away.
His technique was flawless. His timing impeccable. It was as though he knew exactly what to say at the precise moment his words would cause the most devastating result. His actions, both subtle and ostentatious, were equally magnificent.
Often he wasn't fully aware of what exactly it was he had wrought until well after the fact. Some might call it a natural gift, possibly dumb luck. His victims preferred to label it as ignorance or raging stupidity.
Regardless of your point of view, the end result was the same: he'd sabotaged yet another promising relationship.