gone bad

Short definition from Wiktionary

Verb

1. 1
   past participle of go bad

Adjective

1. 1
   Of foods and commodities, having become spoiled, rotten, or otherwise unusable due to age or storage conditions.
2. 2
   Of a person or entity, having ceased to be reputable and having instead become delinquent, criminal, or poorly behaved.
3. 3
   Of a region or area, having become unsafe.
4. 4
   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.