"You are a sh!thead, Williamson". This gets me every time. Just Lemmon's casual delivery. As if he's reading a statement of fact from a textbook. It comes right on the back of Roma's lengthy, vitriolic putdown.
Williamson's brief pause...realising that sleaze Levene was using '..my daughter' to save his own ass...and then delivering the best *beep* you!" ever on film.
I also liked his line before that. "Because, I don't like you". It was such sweet payback after he was abusing Williamson the whole movie.
You close and this whole place stinks with your dumps for a week--how much you just ingested, OH! WHAT A BIG MAN YOU ARE! Your pal here closes, and all that comes out of your mouth is bile! Eeeyah! How *beep* up you are! I'll give you a pack of gum and I'll show you how to chew it!
And later:
You are here to help us! Not to fucx us up! You want to learn the first rule? You'd know if you ever spent a day in your life: you never open your mouth until you know what the shot is.
When Roma and Link are talking about the 3 day rule for cancelling a deal and Roma says when talking about the rule "I know, I was on the board when we drafted it".