I think it's worth mentioning that a pool large enough to do malicious things on the chain and get away with it is strongly disincentivized from doing so.
It would take billions of dollars worth of ETH to do such a thing, and then doing it would destroy confidence in the coin and absolute tank the price, costing the evil pool hundreds of millions.
> doing it would destroy confidence in the coin and absolute tank the price
People seem to say that but there's no evidence of this in fact. A price will only tank if lots of other holders rush to sell before the thief sells his stolen billions.
I think it's a matter of how quickly the thief could make their profits before people notice.
Of course, keep in mind that for such an attack to work, you need 51% of the total ETH being staked. Again, that's billions of dollars right now. If you stole some coins via double-spend, you couldn't pull the money into usable fiat very quickly. Even dumping a bunch of coins is going to crash the price.
It would take billions of dollars worth of ETH to do such a thing, and then doing it would destroy confidence in the coin and absolute tank the price, costing the evil pool hundreds of millions.