That's the one mistake Mendoza ever made. He killed him personally.
4 seconds sound clip from the The Enforcer (1951) movie soundboard.
You can hear this line at 01:09:11.096 in the Blu-ray version of the movie.
Quote context
[...]
- Suppose I give you the top man?
- Your boss? The man who calls you on the phone?
- I take orders from a guy by the name of Albert Mendoza. And I can give him to you for murder.
- That's what I want. I want him in the chair.
- I'm the one guy that can put him there.
- You ever hear about a poor slob named John Webb?
- That's the one mistake Mendoza ever made. He killed him personally.
- How?
- Mendoza and me are very close. I've been with him ever since the beginning.
- This guy Mendoza was chiseling in on my boss. Trying to run a little book of his own.
[...]