Sort of a tough one, and I’ll assume you are talking about red chili, not green chili. Will also assume you’re making it pretty mild so the wife will eat it.
Typically I put all my seasoning/flavor in while making it. I really like the flavor of Chili-O packaged seasoning. It isn’t particularly spicy though and it prob wouldn’t be as good added after the fact. To up the heat, I add jalapeños, cayenne pepper and tabasco (or other pepper sauce). Too much tabasco will give it a vinegar flavor which may not be wanted. I guess my best suggestion to make it spicier would be red cayenne and/or white pepper. Shouldn’t change the flavor profile too much but will add spice.