The lats are not the only muscle that contributes to the “V-taper” look! You must also display wide, round, melon-like delts if you want to drop some jaws in the gym and on the beach. The side lateral raise, in all of its forms (seated, standing, cable, machine), is perhaps the best builder of the medial deltoid head, which is what creates the width on the side of the shoulders. I use side laterals every time I train delts.
Tips: Very few people do this exercise correctly, mostly because they use too much weight and lift via momentum and not muscular action. Perform laterals strictly, with no torso swing, if you want to truly isolate the side delts. Keep the hands flat to the floor at the top of the movement and maintain a slight bend in the elbows at all times.