Penalties for rent not paid

Hello everyone,

My wife and I bought an apartment 13 years ago, lived there for 5 years and left when we had our first child. We rented it and our tenant has accumulated about 114000CHF of unpaid rent over the 8 years he lived there (we applied a 3% on what he owes us over the years).

I never really lost faith in the fact that he would pay at some point because he had some problem getting his hand on his money (inheritance dispute).

He is about to pay and we are wondering what kind of penalties we can applied on the total amount in order to make up to all we had to go through during these year (having constant negative amount on our personal bank accounts, being stressed all the time having to pay penalties on our day to day invoices because we needed more delay to have enough money, etc.)

Thank you in advance for your help.