Far gone
Definition 1 of 3
Pro Tip 1/3Neglect Indication
Use 'far gone' to describe something severely deteriorated from lack of care. 
The neglected garden was far gone with overgrown weeds.
Pro Tip 2/3Beyond Repair
Implies an object is too damaged to fix, often used for buildings or objects. 
The car after the accident was far gone.
Pro Tip 3/3Severe Illness
Can refer to a person whose health is severely declining, seemingly beyond recovery. 
Grandma was so far gone the doctors had little hope.