but as an ethical thing to be done then he is really worth on getting something because exposing some bugs or something like that.
Based on Bithobo support's clarification earlier, it seems like he didn't inform them about the bug at all. He simply took advantage of it in order to win a lot of games and tried to withdraw his winnings which Bithobo refused.
If this is the actual truth, the ethical thing to do here is to ban him from their site and improve the security of the site drastically in order to prevent more such cases asap.