What is the best diet for weight loss?

There aren't necessarily any foods or diets that are best for weight loss. Most simply, weight loss is about how many calories you consume compared to how many you expend. Your body needs a certain amount of calories, and if you consume more or less than it needs, that will result in weight gain or less, respectively.

If you are restricting calorie intake with the goal of weight loss, you should focus mostly on healthy foods that are nutrient dense and lower in calories. These are foods like whole fruits and vegetables, lean protein sources (lean meats, protein powder, tofu, seafood, eggs/egg whites, beans), low fat or fat free dairy products, and whole grains such as brown rice, whole wheat bread/pasta, quinoa, popcorn, etc. These foods are all going to give you nutrients to keep you full and supply your body what it needs, while avoiding extra calories.

There are other foods that are still healthy, but have greater caloric density. Foods high in healthy fats like peanut butter, nuts, seeds, avocados, and plant oils should be included as long as you're careful about the portion sizes. 

Remember that each food can have its place in a healthy diet. Even less healthy foods can be included in moderation and on occasion.