So bitcoin as the ur-crypto has a bit of an energy problem. The problem is that it is built in by design as the primary defense of the system.

If you can control more than 50% of the processing you control the entire currency. So the energy cost has to be high enough to not be worth it.

So as bitcoin becomes more valuable the processing cost has to go up as a security measure. This means that the cost of transactions goes up with it though.

For a coin to become a global currency it needs to cost more to corner the processing than any single entity could achieve, so the processing energy consumption has to be higher than the US govt or the Chinese govt could hope to match.

This energy cost has to be on going, it can't be a one off like building a fort around your gold.

My question is, are there any decentralized coins yet that don't have a 51% problem?