I have not gone into much details of your problem, i don't know if you got scammed or trying to scam but I skimmed real fast though the comments and here is a thing you should know

- You still reserve the right to file a lawsuit even after accepting compensation as long as you have not signed a legal agreement that forbids you from suing them for the exact same case , if you signed on something like that, then it's game over, if not ! then you can still demand your 20btc + compensation.

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depending on the proof / judge and what law-zone the website is obligated to follow your chances of winning the case can vary from guaranteed to nothing.
20BTC is a lot of money, call a lawyer and seek advice, but keep in mind if you are attempting to b.s and they can prove anything against you, you can be in deep shit too.

however there are two things i find "funny" from both of you

This goes to you .

1- why did you wait all this long to post on scam accusation, and if you were 100% sure you are right, why did you accept a compensation of 0.2btc only?

This goes to  FortuneJack

2- if you were so sure this player was abusing a bug on your system, why did you have to compensate him + give him his deposit back?