Ethereum Classic is the original protocol of Ethereum. As a result of the massive hack on the Ethereum-based DAO, in which around 14% of all ETH in circulation were stolen, a hard fork was proposed to return the stolen funds to their owners. This caused an ideological split revolving around the question of changing previous transactions in the blockchain. Some Ethereum holders rejected the hard fork, and decided to keep using the original protocol, based on the principle that the blockchain is immutable, and cannot be changed.

Apollo is developing an all-in-one cryptocurrency platform, based on the APL coin. Apollo was created as a fork of NXT, and has a very ambitious plan to integrate a variety of services under one platform, with a strong focus on privacy. Apollo's blockchain is called Hermes and has a Proof-of-Stake consensus mechanism. Some of the features that Apollo's marketing materials claim they are working on are: private transactions with IP masking, smart contracts, encrypted messaging, file sharing, a decentralized marketplace, voting system for governance, decentralized data storage, and a wallet with a built in exchange. John McAfee, a notable blockchain enthusiast and antivirus pioneer, joined the project in October 2018.

ZCoin is a privacy focused cryptocurrency built on Ethereum. The ZCoin protocol enables anonymous transactions with cryptography that utilizes Zero-Knowledge Proofs (ZKP). ZCoin increases privacy on their network by using a coin-mixer contract that wraps transactions in a serial number and destroying wrapped coins once they have been redeemed.
Zcoin was the first cryptocurrency to use a Merkle Tree Proof (MTP) as its proof of work algorithm. Merkle Tree Proofs are an innovative solution to achieving network consensus, and can increase transaction time while reducing the centralizing tendency of ASIC mining.