Why Gurkha's early loss was not simple failure

Which Tribal-class destroyer had the least successful career?

Technically Gurkha because she sank first, although she did so while protecting a convoy from an air attack.

Gurkha was the first Tribal-class destroyer to be sunk, making her the least successful only by the narrow measure of survival time. She was lost while charging an air attack and preventing the aircraft from reaching the convoy. Her sacrifice gave the escorted ships a better chance of escape. An early loss can still reflect effective and aggressive escort work.