Nah, there is no worst..
Before the advent of ERC20 enabled ICO, there was a trend of scam coins people called Shitcoin.
A Shitcoin is a low effort fork of any of the POW coins back in the day, with no whitepaper or real world usage of any kind. Their only strategy was to create a coin out of thin, get it listed on Cryptsy (it was that long ago), and then use it as a vehicle for pump and dumps.
It's estimated that at one point a few hundred new types of shitcoin gets created every single day.
Knowing that there are probably hundreds of thousands of such coins, it's hard to point finger at the worst cryptocurrency...
According to WEISS RATINGS they make 12 worst crypto currency list and published. I have shared this list bellow you can check. But in my opinion every crypto currency is worst until they have not working product. Only good cypto for investment is who have working product and the team are come with genuine project, the project will help the world for solve problem through blockchain. The product need use-case all these project are good other wise don't invest in those coin who have product on paper only.
Here is worst coin list provided by WEISS Rating:--
The latest value according to the agency with a Cryptocurrency rating from D- or lower includes the following twelve:
Electroneum (E +),
It should be noted, however, that Weiss Ratings often updates its ranking so you have to check their website regularly for the latest values.