You are never _guaranteed_ to win a race against honest block producers for any finite time horizon, even if you owned 99% of all hashing power.
A double spend via 51% isn't really feasible anyway. A double spend attack, in the simplest case, is to:
1. Pay for good or services
2. Receive delivery of the goods or services
3. Invalidate the original payment once the goods or services are no longer revokable.
For a double spend to be worthwhile the value of the scam must exceed the cost of the scam. Maintaining >50% hashing power is extremely expensive and is more and more expensive the longer you maintain it. Therefore the value of the scam must also be extremely large. For crypto transactions it's common sense to wait for more and more confirmations (additional blocks mined after the block containing the transaction) before delivering the goods or services as the size of the transaction grows. Since it's trivial to wait for N+1 confirmations as the seller of goods or services it's trivial to defend against double spends for any meaningful amount of money.
A double spend via 51% isn't really feasible anyway. A double spend attack, in the simplest case, is to:
1. Pay for good or services
2. Receive delivery of the goods or services
3. Invalidate the original payment once the goods or services are no longer revokable.
For a double spend to be worthwhile the value of the scam must exceed the cost of the scam. Maintaining >50% hashing power is extremely expensive and is more and more expensive the longer you maintain it. Therefore the value of the scam must also be extremely large. For crypto transactions it's common sense to wait for more and more confirmations (additional blocks mined after the block containing the transaction) before delivering the goods or services as the size of the transaction grows. Since it's trivial to wait for N+1 confirmations as the seller of goods or services it's trivial to defend against double spends for any meaningful amount of money.