I can only suggest you test one by one of all casinos here to find the right casino you want because today, it is difficult to find a casino where you can bet 50 BTC. Besides that, playing with 50 BTC is too big and even if Stake allows you to gamble with 50 BTC, your profit is just 5 BTC, as @seoincorporation said and that is not worth doing. Using 50 BTC to gamble will make casinos suspicious as they rarely have gamblers who gamble with that such big BTC amounts. So it will make them ask you to verify your account and make sure you are not doing illegal things.
There's no crypto casino that accepts this kind of huge bet for a 50/50 chance rate as many already point out so there's no need to try it one by one because it will just a waste of time and this is hard because some casinos have wagering requirements on deposit so OP will be obligated to wager that amount slowly before he can withdraw while that is risky. I assume OP already check many websites that's why he comes up creating this thread and ask instead to save his time. The OP is involved on shady activity we should not take this inquiry seriously because he might just using this thread to let us know that he still has a huge amount of BTC after all his shady activity in the past.
Look at this
I'm still here because I didn't do anything wrong. I wouldn't have tried joining a signature campaign if I was sitting on millions of dollars of bitcoins, lol.