Does a bad actor need 51% of coins on a PoS network to disrupt it?

I'm seeing conflicting information on what % of stake an attacker would need of a PoS chain's coins to disrupt the network. With PoW chains, an attacker needs 51% of the hashrate. Would you need 51% of coins on a PoS chain to successfully disrupt it or fewer than that? Or is it 51% of the amount that is staked of the circulating supply? Or is it less?