VA-111 Shkval

Well, the Japanese WWII torpedoes should prompt a lot of fear. They were the best Naval torpedo of any world power during the entirety of WWII, and were part of the reason for the massive damage at Pearl Harbor; U.S. Naval officers assumed torpedoes couldn't operate in a harbor that shallow, but the Japanese had developed a way around it.

Likewise once the Americans fixed their own multiple torpedo flaws by summer 1943, American submarines became very deadly in the Pacific.

However your questions regarding the VA-111 are valid. The flow noise generated from moving so fast (and with a gas bubble to boot) means that the VA-111 should not be able to hear the target to move in on it. This would require guidance from the launching platform's sonar, but I don't know of any guidance wire that would survive that trip.

Instead the torpedo seems to require a very good firing solution before the shot is made, to allow the INS to bring the torpedo to the target before they can evade. Even then you'll likely miss, which seems to be why the nuclear warhead option was chosen.

With modern non-nuclear versions it would seem that terminal guidance would require a separate (much slower) phase of operations, which might very well be susceptible to acoustic countermeasures.

Additionally it was created as an ASW weapon, not ASUW, so the warhead capacity seems to be too small for a high probability of kill against a surface ship, unless they can indeed detonate it right under a keel. On the other hand it would be easier to get a good target solution for a surface warship since it's a 2-D geometry instead of 3-D.