Which fat is the most unhealthy?

Willet: Some types of fat are healthier than others. Unsaturated fats are the healthiest fats . Vegetable oils, such as olive oil, rapeseed oil, corn, peanuts and other nut oils; nuts, such as almonds, peanuts, nuts and pistachios; avocados and fish, especially oily fish, such as canned salmon and tuna, …