Guest ask for partial refund because of smoke odor

[Luke224]

So. I have an apartment, and one of our longer tenant has been smoked in there, which caused the odor hard to remove. 

We have tried many things to get rid of it include viniger and baking soda on fabrics and walls.

The guest who is living there right now(3days) are complaining about it, and says one person in his group are very sensitive to it.(Although the smoke odor is much weaker than the very beginning) and wants a partial refund.  He says he wouldn't book it if my listing says there is smoking odor（who gonna mention it....)

To be honest, he is not the only one complain the smell, but most of them just complained a little bit and thats it. 

I will only operate this 2bd Airbnb till the end of next month and close it.

And I know even I offer some discount to him at this stage, he will still give me poor rating. 

I want to hear some suggestions from the community, and if you suggest discount， how many percent should I offer?

What would happen if I denied his request?

Thanks

[Rachael171]

I have a positive update on this. Air bnb support gave the guest a full refund but funded me for 2/3 of the stay to help with my losses. They also cancelled the reservation and freed up my calendar. It took about 24 hours to get this resolved through air bnb, but things moved way faster when I called them instead of texted.