Let me give you a brief overview of those multi-hit walls. The notable case was in volcano manor, behind the drawing-room passage which needed around 50 hits to break through. While it seemed like an intentional feature at first, dataminers discovered it had 9999 hp instead of the usual single-hit script which made things interesting.

Good to know though, this specific wall got patched out in update 1.04, so you won't find it anymore. Most illusory walls follow the standard one-hit rule now, and that volcano manor path was just a shortcut to an already accessible area anyway. If you're wall hunting, margit's shackle or law of regression can reveal hidden paths instantly which is much more reliable than testing every surface with multiple hits.