I want to stand on the roof of the tallest building I can find & scream at the top of my lungs,
"I TOLD YOU SO!!"
But that might not go over so well.
It tends to make people (who know they've been made a fool), well - defensive. Best to try & get those people back on your team. Best to give them a way to save face while admitting the error of their ways...
While pointing the harsh finger of incrimination, it's best to
try a little humor: