You could make an attack if you control more than 1/3 total staking value of the network.
But as Bart said: “however if you can within an epoch purchase 1/3 of a single validator set, you can in essence compromise the entire network”
Dan answered: " You could, but you gotta find them, get them to agree, then you gotta trust they don’t just take your money.
Plus they will get slashed if they do anything but abstain to cause a liveness break, so you’d have to cover their stake too plus making it worth their while
Liveness and safety issues only cause issue on anything that touches that validator set. All actions that don’t still run just finr"
You can follow the thread for more information regarding the attack on the specific shards that those validator set validate on the specific epoch: Telegram: Contact @radix_dlt
Still, since all the things is randomized, you will never know which shard your “compromised validator” got assigned to in the next epoch