Fiii Coin is developing an ecosystem designed to promote the wide spread adoption of a variety of cryptocurrencies. Their payment terminal will be compatible with wide range of cryptocurrencies, and will be comprised of a wallet, exchange, and DApp development plugins. The Fiii blockchain has a Delegated Proof of Capacity (DPoC) consensus mechanism.

Litecoin is a crytptocurrency that was created to serve as the “silver” to bitcoin’s "gold." It is based on the core Bitcoin protocol, but was designed with several key features that provide it with advantages over Bitcoin.
Litecoin has significantly reduced transaction times by limiting the target block processing time to 2.5 minutes. It also has a total coin supply that is 4 times larger, and utilizes a different hashing algorithm called Scrypt, that requires a smaller workload and less computation power than Bitcoin's SHA-256 algorithm. This enables much faster transactions at a much lower cost to users. These features make Litecoin easier to use and to mine. Since its creation, Litecoin has gained a large market cap and widespread adoption among cryptocurrency users in need of a coin for everyday transactions.

BitcoinDark is a fork of Bitcoin with a poorly defined purpose and use case. BitcoinDark is based on the InstantDEX protocol, a decentralized exchange for BitcoinDark and other cryptocurrencies supported by the project. The platform is also supposed to include a Pegged Asset Exchange (PAX) to allow users to buy and sell pegged assets – including fiat currencies, commodities, ETFs, and stocks.
BitcoinDark is a Proof-of-Stake (PoS) currency that has gained a significant market cap, but the project has failed to show how its vision will be implemented or how it will add value compared to other blockchain projects.