gone bad

Of foods and commodities, having become spoiled, rotten, or otherwise unusable due to age or storage conditions.

Of a person or entity, having ceased to be reputable and having instead become delinquent, criminal, or poorly behaved.

Of a region or area, having become unsafe.

Of a delinquent or criminal act, having unexpectedly become more violent than is typical for that act—having resulted in an attack on a victim leading to serious injury or death.