Final answer:
Bereavement due to widowhood is the factor that most increases the risk of an elderly person suffering mistreatment. This can lead to increased vulnerability and susceptibility to mistreatment, both physically and emotionally.
Step-by-step explanation:
The factor that most increases the risk of an elderly person suffering mistreatment is bereavement due to widowhood. When an elderly person loses their spouse, they may experience increased vulnerability and be more susceptible to mistreatment, both physically and emotionally.