The one where he threatened the man into becoming an ethical businessman?
Just to show us what it is that he does for a living?
Are we supposed to know who his employer was that time?
No, because his employer wasn't John Lithgow's character. It was just an exposition scene to showcase who he is and what he does.
shareI think partly to show his unarmed combat skills, even though he is relatively small.
There was perhaps also some "moral code" to his behaviour ; although he was probably hired by people with very large holdings of shares.
Spoilers
It was this scene which led me to realize they were brothers. Showing the fighting skills of a yet unknown character and then the fighting skills of the brothers growing up. For me, it was a let down that I had figured it out.