You can always be sure if you do some research. Yes, it may not be 100% guaranteed but at least you will get something pretty close. There is no coin that will not get all the necessary details you will need and the same way we get to know coins that will end up being a scam is the same way we can get to know a coin which is centralized which is totally by doing some little research about the team, the idea of the coin itself and so on.

The research for worst coin may go infinite as only very few coins are coming up with a reason and all others are just a copycat or simple modified concept of some other existing projects. If we notice in depth, now a days altcoins are here for fund raising for a project but there will be no guarantee that project will go live or not.