A cat’s claws are too long when they develop into a curved shape. In extreme cases of overgrowth, the claws can curve into your cat’s toe pads, which can be painful and cause open wounds.

That is an extreme case, and I think that is required pain here.

most of these things seem to indicate to me, the said cat is not doing play/scratch/hunt/climb enough. Many comments speak of this, but i think cats gradually and naturally wearing claws is better than discreetely done