It's really easy. Use casinos in 3rd world countries to certify your money as gambling winnings. There must be underground network for this. So it looks like you're gambling and you got lucky. Very dangerous though. I heard that they charge 13% total fee. You come in at 5M$. You play for 1 week.. Leave with 160M or something. Bring that cash into the bank and deposit it.
I still think you’d get under an investigation (at least from the tax authorities, but I can imagine police too) after years of years consistently depositing millions of wins in your bank account.
I do not think shady people put their loot in bank. Most illicit activities and tax avoiding folks rely heavily on cash or other expensive exchangeable goods(rolex/jewellery/gems/gold bars/gold watches etc).
