probably the worst blockchain technology usage is by ethereum. they have ruined a lot of things for this technology! starting with the decentralization which they advertise as but in reality it is very centralized. then they also killed the immutability of the blockchain technology by performing a roll back...
in any case that was the answer to your comment but to address your title question i believe one of the most interesting technologies based on blockchain is DAG. there are currently a dozen of them around and this way of using it seems to have quite a lot of potential for faster speed and cheaper transactions. although they lack decentralization.
DAG is a rather promising technology but it's not a blockchain. And I'm not agree with you that Ethereum is very centralized, it's not so.
