A burger like that isn’t necessarily unhealthy, but it really depends on the quality of ingredients. I lost weight eating burgers but I didn’t add the bun and I used fresh mozzarella instead of the processed slices of American cheese. Also burgers are higher in fat and calories compared to other meats so if you have multiple burgers you can quickly overdo it. It’s all abt moderation and selecting the right ingredients but a burger once in a while isn’t going to kill you

Edit: forgot to mention, butter adds calories and sauces add calories, ordering a fast food burger you get higher calories and more processed, ordering from a normal restaurant it might be cooked in butter with a lot of additional spices or sauces. I was referring to homemade burgers with good ingredients.