It implies a strong, almost reckless commitment to a goal.
Here are some examples:
* "She was hellbent on winning the race, even if it meant breaking her own record."
* "He was hellbent on getting revenge, no matter what the cost."
* "The government seemed hellbent on ignoring the warnings about the impending crisis."
It's often used in a negative way to describe someone who is acting impulsively and without regard for the potential consequences.
Origin:
The phrase originated in the 16th century, when "hell" was often used to describe something extreme or dangerous. "Hellbent" literally means "determined to go to hell" for the sake of achieving a goal.