Kind of a fun Odd Couple Trivia game! Note that I don't know the answer myself but this should be interesting! I have listed some episodes where each made threats to the other, for example:

In "You Saved My Life" Oscar tells Murry "Felix is alive isn't he that's being tolerant." and I think he also says, "Would you look the other way if I killed him?"

In "Trapped!" where Felix, Oscar, and Nancy are stuck in the cellar Felix says, after Oscar let's go of the rope and the dumbwaiter falls with Felix getting bruised from the fall he says he's hurt. Oscar says he's over-reacting, and Felix says, "I'm not over reacting, and if you say that again, I'll bash your skull in!"

What others?

Jack

Kind of a fun Odd Couple Trivia game! Note that I don't know the answer myself but this should be interesting! I have listed some episodes where each made threats to the other, for example:

In "You Saved My Life" Oscar tells Murry "Felix is alive isn't he that's being tolerant." and I think he also says, "Would you look the other way if I killed him?"

In "Trapped!" where Felix, Oscar, and Nancy are stuck in the cellar Felix says, after Oscar let's go of the rope and the dumbwaiter falls with Felix getting bruised from the fall he says he's hurt. Oscar says he's over-reacting, and Felix says, "I'm not over reacting, and if you say that again, I'll bash your skull in!"

What others?

Jack
I would think the natural answer would be Oscar..

But Felix had a few outside of the scene you mentioned..

When Oscar made fun of Felix on TV Felix screamed at him.. "The whole world thinks I'm a neurotic madman and I'm gonna kill you for that'!!!