A conventional missile or even missiles is not going to destroy a huge gravity dam like that. They are incredibly tough structures and missile warheads aren’t big. We’re talking concrete hundreds of feet thick.
To add some background. During WWII the allies successfully used massive specialized depth charges but those were much smaller dams. [0] During the Korean war the US struggled to merely destroy the sluice gates of a dam using aerial torpedos. [1] Eventually the Geneva Conventions were amended to forbid attacking dams if it would kill a large number of civilians (which was pretty obviously implied to begin with for what it's worth).
So unless Taiwan has a method to deliver something the size of a bunker buster to the underwater base of the upstream side of the dam I don't think it's going to happen. And if they did manage to pull it off they'd presumably be condemned as war criminals more or less universally.
To add some background. During WWII the allies successfully used massive specialized depth charges but those were much smaller dams. [0] During the Korean war the US struggled to merely destroy the sluice gates of a dam using aerial torpedos. [1] Eventually the Geneva Conventions were amended to forbid attacking dams if it would kill a large number of civilians (which was pretty obviously implied to begin with for what it's worth).
So unless Taiwan has a method to deliver something the size of a bunker buster to the underwater base of the upstream side of the dam I don't think it's going to happen. And if they did manage to pull it off they'd presumably be condemned as war criminals more or less universally.
[0] https://en.wikipedia.org/wiki/Operation_Chastise
[1] https://en.wikipedia.org/wiki/Hwacheon_Dam