At one end of the spectrum, we have cryptocurrencies like Bitcoin and Ethereum, which are known for their high degree of decentralization.
You probably haven't heard about the roll back of Ethereum transaction to save the ass of a DAO from a hack although Vitalik Buterin doesn't agree that it wasn't a roll back; they intervened. Whatever it was, it was centralization.
Is this what you call decentralization? LOL.
https://bitcoinist.com/ethereum-network-not-rolled-back-after-dao-hack/