What is the most heartbreaking betrayal you've seen in the workplace?

The most extreme one I've witnessed was from a project manager who had been working at a publicly listed company for nearly ten years.
He led a team that created the company's biggest hit at the time.
As a result, the project was taken by higher-ups, the team was sidelined, and the boss patted him on the shoulder at a meeting, saying it was a strategic adjustment and to wait a bit.
He didn't argue, but the next day he left a resignation letter on the desk, saying, "Fine, I'll step aside."
Then came the turn of events.
Less than a month after he left, the new person in charge of that project lost the core data.
The client went into an uproar, and even an overnight company meeting couldn't resolve it.
The boss was frantic, trying to find him everywhere, hoping to bring him back to save the project.
His conditions were very simple: it didn't matter whether he apologized or not, just give back the project leadership, and remove the person who was parachuted in initially.
The boss was silent on the phone for two seconds and then said, "The company has decided to bring you back."
On the day he returned, the entire team stood up and applauded him.
The new person in charge sheepishly packed up and left, and his computer password has never been changed since—it's still that phrase, "just do it."
He changed it to a new phrase: "just done."