A 51% attack represents the situation where more than half of the computing power
The attackers would be able to prevent new transactions from gaining confirmations, allowing them to halt payments between some or all users. They would also be able to reverse transactions that were completed while they were in control of the network, meaning they could double-spend
They would almost certainly not be able to create new coins or alter old blocks. A 51% attack would probably not destroy BitcoinBitcoin1$ 77,295.840.18%-6.01%-15.89%details or another blockchain-based currency outright, even if it proved highly damaging.
Those who cannot attack the thought, instead attack the thinker.