In 2018 I only knew Dash, Nano, monero and Neo with coins that had super fast transaction speeds. but actually many are faster than that, because more and more coins are popping up, for example Idna, Ark, Icx if you compare the transaction speed then they could be the winner.
Basically, any cryptocurrency has blazing-fast speeds if the network is not congested. For once, Ethereum used to be one of the fastest cryptocurrencies in the world. But after mainstream adoption grew, its speeds were never the same. Of course, some cryptocurrencies have more efficient consensus algorithms than others. My guess is that the fastest cryptocurrencies are those using "DAGs" as their backbone. Coins like Nano, IOTA, Hashgraph, and Constellation could be considered the 5 fastest crypto coins right now due to their use of the "DAG" algorithm. DAG-based cryptocurrencies have fees that are ridiculously low (sometimes even free), while transactions settle almost instantly on the network. Yet, the aforementioned cryptocurrencies sometimes sacrifice security/decentralization on top of performance. Which is why I believe that depending on your needs, will be the type of cryptocurrency to use in the mainstream world.
Nonetheless, most people will continue to support cryptocurrencies like Bitcoin and Ethereum even if they struggle with high fees and slow transaction confirmation times. This is largely because decentralization and censorship resistance is what matters above all else. The fastest cryptocurrencies in the world might survive for a long time, but their level of adoption will never surpass that of Bitcoin and Ethereum. Ultimately, people will decide which cryptocurrencies to use from the other depending on their needs. Bitcoin works great as a store of value, but it's terrible as digital cash. The contrary happens with Ethereum. At least, crypto will be here to stay for a very long time. Just my opinion
