Ethereum classic is the best altcoins to invest for huge gain before 2018
In 2017
New Monetary Policy (ECIP-1017)
Emerald Wallet
Dapp SDK (based on Emerald Project)
Standalone & embeddable EVM (with debugger for EVM code)
In 2018
Light client for IoT and Mobile
Scalability improvement and sharding (towards to 1,000+ tx/sec)
Improve cryptography on EVM (for zero knowledge proof, homomorphic encryption, etc)
I also believe ETC is currently undervalued. It has great potential to do 2-5x from here within the next 6 months. But I feel the price will go lower than this as I believe ETH dump is still not over and this will impact the price of ETC.