Yes, Cardano is know as an ethereum killer.Today, smart contracts will be implemented in Cardano. This is certainly a milestone that will determine whether the project will be successful on a larger scale in practice.
Since both Cardano and Ethereum are undergoing significant changes, it is difficult to say which one will turn out better. Cardano may come close to Ethereum in terms of market capitalization, but future events will determine whether it is hailed as the killer of Ethereum.