Optimism excels at maximizing Ethereum's security inheritance through its fault proof system (currently transitioning from a multi-signature to a permissionless model). This design treats the L2 as a simple, verifiable extension of Ethereum, where any invalid state can be challenged. The security guarantee is direct and battle-tested, with the OP Mainnet securing over $6B in TVL. The trade-off is a longer, more complex withdrawal period (up to 7 days for full security) and higher on-chain verification costs for complex transactions.