There's no singular magic exercise. Pick six exercises and do 3 per workout (and the other 3 the next workout) if you want to him 'em hard, bis after back and tris after chest imo. Vary the rep scheme as well, heavy 4-6 for two weeks, moderate 10-12 for two weeks. Record your lifts and add weight each time, even if it's only 1 lb, or get an extra rep or two. If you consistently get no progress with adding weight or reps, look at your diet, sleep, and hydration. My training knowledge sucks compared to some guys here but that's what I'd try for lagging bodyparts.