As a urine removal specialist in Tampa FL I come into homes with severe urine damage in many areas. I not only fix the damage caused by the pet, but I have deal with the damage caused by the home owner trying different solutions to get rid of the urine stain.
In the photos above the urine damage is pretty severe. The before picture shows the urine stain and the amount of scrubbing that was done by the home owner to get rid of the urine in the carpet. The area looks pretty beat up and is considerably darker than the rest of the carpet. After treating the urine to eliminate the smell the area was sanitized and then cleaned.
In the after picture you can see that there is a slight lightening of the carpet. This color loss was caused by either the urine itself or the cleaning product used by the home owner to clean the urine. It's not unusual for the urine in the carpet to urine bleach or urine burn the carpet. The damage can be corrected after treating and cleaning the carpet. In this case the home owner decided to leave the bleaching it alone because they were putting the home on the market and didn't feel it was going to impact the sale price.
As a urine removal specialist I know this kind of severe urine damage can be repaired and the carpet can be saved but it always up to the home owner on what they want done on the carpet.