[hjorthjort]

An important and often misunderstood point:

Having >2/3rds of validators (or >50% of power in PoW) let's you rewrite the chain back in history, censor txs, etc. You control what transactions go in blocks, and to a certain extent also recent history.

HOWEVER, this does not give you the power to steal or rewrite state as you please. You cannot convince the rest of the network that you now own someone else's ETH just because you have supermajority validator power. To take away ETH or change the cabin state in any other way, you need to include a valid and correctly signed transaction.

If you include an invalid state change (not caused by a successful and correct transaction) then all other nodes will reject that block, no matter how much validator power or hashing work went into it.

[rakoo]

Well this is the same as any blockchain: you can't forge a block with a transaction giving yourself money, but you can double spend the same amount to multiple other accounts. Unless something is different with ETH which I don't know enough

[cypress66]

Double spends are actually much harder here, after slots are finalized (2 epochs, about 12 minutes) but yes it's the same as other blockchains.