ETH if we will be talking about altcoins. There is no other altcoins except ethereum has high yield for now following bitcoin. However, I think before the bitcoin bull run there are news about other altcoins with low supply that has been easily pump up by the investors letting small time investors earn more. YFI was the name of the coin. Well, good for those who were able to participate in that coin. Pretty sure it is one of the high yield altcoins havin a price of more than 30K$ per YFI.