The score is pain points, so if you use traps - it will case pain - you will get pain points. So, fire & traps are both pain causing agents.
1. If enemy falls in fire, you will get very high pain points. So basically use as many traps as possible on the enemy and make the enemy falls in fire with as low health as possible to max out pain points.
2. If the enemy dies early (before falling in the fire), you will miss out the fire pain points.