To impair or destroy the value or quality of; ruin.
"spoiled the dish by adding too much salt; spoiled the party by getting into an argument."
To harm the character of (a child) by overindulgence or leniency. synonym: pamper.
Similar: pamper To plunder; despoil.
The American Heritage® Dictionary of the English Language, 5th Edition • More at Wordnik
How is that “spoiling” someone?
spoil /spoil/ intransitive verb
The American Heritage® Dictionary of the English Language, 5th Edition • More at Wordnik