I’ll say NXT.
NXT is a clear example of a gem that lost its sparkle. One of the first proof of stake cryptocurrencies. Was doing so well with a strong community. But regrettably the development slowed down and the project lost traction.
GMT was favorite altcoin, I was inspired to see my portfolio counting in good figures during the bullish pump of the altcoin, and I'm scouting for another dead altcoins that will be the next big thing in crypto. These gems are not always spotted in the market, there are so many dumping projects, it's reasonable to spot the one that have good roadmap. GMT made quite good numbers of traders rich and also ruined the portfolio. GMT was one good illustration about projects that can exceeds limits and beats all odds towards skyrocketing to the moon. Dump altcoins are the crude oil in crypto if you ask me. Take a chill pill, calmly predicts how the market operates.
I don't see any dead coin as a gem because it does not worth it to be called a gem when so many investors must have lost their hard earned money. Most of this devs would launch a crypto project and create marketing deals with different websites so plenty investors would put their money in the project, holding it with the plan of the price appreciated in the future. Suddenly they would rug pull the project and the community would be left with nothing. Sometimes it could even stay in the market for more than a year with heavy marketing to increase the popularity of the project before rug pulling and leaving investors in huge regret.