The largest jackpot of all time was a $23.6m bonanza (around 19m) landed by one player from Belgium back in 2024. They were playing the Absolutely Mad variant of Mega Moolah, and no doubt the individual was going bananas when they realised the extent of their win.
You just have to stick to legal, regulated online casino sites such as BetMGM, Caesars Palace Online Casino, FanDuel, Betway, bet365 and BetRivers. They offer great casino game ranges and they will pay out quickly and without any issues if you win.