Ethereum competitor is for me, NEO.
NEO have smart contracts just like Ethereum and it has almost the same features as Ethereum as well like scalability, transaction speed, smart contracts and more.
NEO had more investors and supporters as well and it's backbone is a top notch as well.
But in reality, Ethereum is the strongest altcoin in the crypto market today and was predicted that it will surpass Bitcoin's market cap in the future.