The contending decentralized consensus algorithm is called Proof of Stake, and it works by giving you lottery tickets based on how much wealth you already have.

PoS coin supplies should be avoided, as the production cost or input work is not worth the speculative asset produced.

XRP is a case study in how they've created artificial scarcity and can flood the market with sell orders from their reserves.

https://www.coindesk.com/ripple-jed-mccaleb-settle-suit-over...

They could also just have a centralised service validating transactions. No need to mine, no need for stake. Not exactly a traditional cryptocurrency at that point, but in day-to-day use no different (and rather more attractive to political regimes like Maduro's.)

Also, Ethereum ERC20 tokens, which aren't cryptocurrencies per se, just numbers in a ledger whose updates get embedded within the cryptocurrency (ETH)'s blocks.