What Is the Minimum and Maximum Amount of ETH That Can Be Slashed?

The minimum amount of ETH slashed is 0.25 ETH, which is the "base slash amount." This minimum applies to an isolated slashing event. The maximum amount is variable and can be the validator's entire 32 ETH stake.

The severity of the slash scales with the number of other validators slashed around the same time. A "mass slashing" event, where many validators collude, results in a much higher penalty to discourage large-scale coordinated attacks.