Two photos of the "damaged" Kilo class submarine struck in drydock have emerged from Crimea. This is a pretty good illustration of what is called non-repairable.
Looks like it was hit with two Storm Shadow cruise missiles or one that traversed the length with an impressive exit wound.
Destroying this sub, the B-237 Rostov-on-Don, is a pretty big deal. It is a modern diesel electric drive boat that was commissioned in 2014. Among other ordinance, it is designed to launch land attack cruise missiles and has been used extensively in strikes against Ukraine.
The extensive damage to the two drydocks themselves will also provide an enormous maintenance headache for the Black Sea fleet.