Dear Client,

Being a complete and utter asshole does not make your website get developed any faster, so you can kindly fug off.

So I am pretty fair dev at Java and have been doing freelancing for sometime apart from normal full time job.
Got a client , a well funded one, who raised a decent chunk of money recently.
Got me do a couple of different areas right from refactoring and bumping their performance to all the way setting up AWS Services like RDS,Lambdas,Dynamo,SQS.
It was going good , money was coming in for the initial part.
Thinking that money is not the concern here , I accepted work at runtime and gave quotations about the additional work.

However now that all is done and deployed , the client simply refuses to pay me the money and has ghosted me horribly than my ex ever did.

I have access to their GitHub,AWS(I setup myself).

Need suggestions of whats the best way I can fuck them up if they decide to not pay even after a few more professional polite attempts I do .

sidenote : They had a pretty dumb db design and blindly had resorted to services in AWS and the pricing is still a major point of concern for them.