Which altcoins from the last few years where there was a lot of positive talk about it has failed? And by failed, it means either it has went to 0 or it could be worth very little. Like it could been 50 dollars at one point and now 0.50.
Also I am talking about coins that were at least in the top 50 or top 100 in coinmarketcap and then it just fell apart. I don't mean a coin that came out and everyone had praise of it and it didn't even break the top 100 on coinmarketcap.
In my experience, it was PundiX. From 10$ to now 0.7$ and from top 50 to now top 270+ in CMC. The problem occurs when they migrated to new smart contract by which investors didn't like that time added by the fall of BTC. Another thing is SOVRYN who got 82$ as ATH last May then fell to 3.9$ as of the moment. I think these two didn't failed and even deliver what was promised. The problem occurs with the market itself where investors didn't feel safe to invest and bears took over.