In HOI4 terms
-2% stability for 2 weeks
-Ukraine gains 1 manpower

In a technical sense they did into the Kursk region (which in and of itself is a massive achievement). But only after a war of aggression had been started against them by the Kremlin.

Already seems a lot more feasible than laying down and accepting Putins terms. I still think that with more support however the collective west can eventually drain Russia of enough resources to continue the occupation.