First of all, Slots are also among in your " Crypto Games " category but I prefer to call them Casino Games because there is also a specific game for the Crypto Games category. Games like Axie Infinity, Sandbox, My De-Fi Pets, and the likes. Now on your question, the answer would be the casino games. To be more specific ; they can be Crash and Mines. Their multipliers are over millions. Slots can only come in second. I think the highest max multiplier slot game that I heard is Tombstone Rip and it was from the provider called No Limit City.
On one hand, I know slots bring in large X's, but it is quite rare and you have to be really lucky. On the other hand, I saw people get massive multipliers on crypto games like Crash after a couple of minutes of playing. So which is it?
Maybe you focus more on Crash games, and that is why you often seen those huge multipliers in them than on slots.