Has a 51% Attack Ever Been Attempted on a Proof-of-Activity Blockchain?

There is no widely documented case of a successful 51% attack on a major Proof-of-Activity blockchain. This is likely due to the high cost and complexity of such an attack, as it would require control over both a majority of the network's hash rate and a majority of the staked coins.

The lack of such attacks is often cited as evidence of the security of the PoA model. However, it is also worth noting that PoA has not been as widely adopted as PoW or PoS, so it has not been subjected to the same level of scrutiny and attack attempts as more popular consensus mechanisms.