The best exercise for purely losing weight is building better habits around eating. One exercise will not help you lose belly fat, neither will one workout. This would be like trying to drain the ocean with a measuring cup. What will help you lose weight is eating in a caloric deficit for a period of time. I’m talkin’ like months. Honestly, working out isn’t even necessary to lose weight. I was able to help my dad lose 30 pounds without doing a simple rep of exercise. The only thing he did was become aware or what and how he was eating and build better habits around that. So rather than focusing on an exercise, here’s how you can build better habits around eating and lose weight. This is called Habit Based Dieting. Workout also is very useful, you can start with some not difficult sets with for example barbell or dumbbells.