You can DDoS normal, non-validating nodes, and if they go offline, they can be unsure which chain is the true chain, because they were not around.. This means your laptop can never sleep, unlike in Bitcoin, where full nodes may go offline and catch up later.

People who control stake can refuse to include (censor) transactions, as there is no market competition for transaction inclusion like in PoW. In PoW, if 51% of network power is censoring transactions, then censored transactions can attach a higher fee, which competing miners will use to buy more equipment and mine the censored transactions.

These are the ones I know about, that I learned in an evening of research.