spoil (one) rotten

spoil (one) rotten

To cause one to expect to receive everything they want by always giving it to them. In this phrase, "rotten" is an intensifier. I think some grandparents believe it's their duty to spoil their grandchildren rotten.
See also: rotten, spoil
Farlex Dictionary of Idioms.

spoiled rotten

Fig. indulged in; greatly spoiled. This kid is spoiled rotten! I was spoiled rotten when I was a child, so I'm used to this kind of wasteful luxury.
See also: rotten, spoil
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

spoil somebody ˈrotten

(informal) give somebody everything they want or ask for: She spoils the kids rotten.
See also: rotten, somebody, spoil
Farlex Partner Idioms Dictionary

spoil

tv. to kill someone. It was Joel Cairo’s job to make sure that nobody got close enough to Mr. Big to spoil him.
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions
See also:
  • spoil
  • spoil somebody rotten
  • spoiled rotten
  • have had it
  • I've had it (up to here) (with someone or something)
  • I've had it up to here
  • what the (blue) blazes
  • and a half