What kind of damage are you talking about in blockchain?
Its just a bunch of computers talking to each other and relying on consensus to make sure all valid transactions go through.
Since the mining code is open source, if a bug is discovered in the code then any capable developer can fix it and once the miners update their program versions to the new fixed version then all is well.
If the miners (people with typically very powerful computers who have installed the blockchain software) fail to agree / reach consensus on some aspect of the system, one creates a 'fork' - basically a modified clone of the existing one then offers it as anew coin. Many other coins such as Bitcoin Cash and Bitcoin Gold started this way - as forks of Bitcoin.
Always remember, the data is decentralized (all miners have the a copy of the data) and the miners operate with full autonomy. The blockchain ledger (history of all transactions ever recorded) is also final and sealed cryptographically. No one - even the creator of the system, can modify those records.