The squat is probably the best calorie burner because it uses the whole body, and a great building block for loaded variations like goblet, front, and back squats.
The lunge is not only great for unilateral work, but also helps with hip mobility and can be progressed by adding weight in the hands.
These are both knee dominant movements.
Hip dominant movements, particularly hip extension will develop the glutes and hamstrings, and help develop “a nice butt.” You can use hip bridges from the floor and progress to putting the feet on medicine balls and stability balls. Even load them with a barbell eventually.
Use various anti-rotation and dynamic stability exercises to engage the core. Remember, the core is not simply the abs. Band shoulder rotations and pallof presses, along with athletic and sport-type movements often engage the core heavily.
Don’t forget the staples like push-ups, pull-ups, and dips. Progress is key as many, especially the overweight, struggle with these movements. Start with modified push-ups, in small sets and progressing to either more reps per set, or more sets. Pull-ups can be assisted by bands to start. And use a chair for dips and gradually work the feet outward.
Along with any exercise program should be a balanced nutrition program as well to help lose body fat.
A similar question posted here at IDEA may give you some insight:
I Hope This Helps!