Has Any Major Blockchain Successfully Executed a Rollback Due to a Dispute?
Yes, the Ethereum blockchain executed a controversial hard fork in 2016 following the DAO hack, effectively "rolling back" the chain to recover stolen funds. This created two separate chains: Ethereum (ETH) and Ethereum Classic (ETC).
This was not a standard contract dispute but a catastrophic security event, demonstrating the technical possibility but highlighting the deep ideological divide on immutability.