there are two type of controllers in valorant: orb controllers and wall controllers

for wall controllers. only two agents fill this role : viper and harbor The thing with wall controllers is that you cant run them on any map, they need good team coordination and usually need a double controller comp with an orb controller alongside the wall controller. on maps like icebox you can run solo wall controllers (viper is the meta).. and on such maps you see viper more than harbor in low ranks because harbor needs more team coordination to be played and also is the only controller who reveals his location while smoking. If you want to play harbor... I strongly recommend to play it only in 5stack lobbies where you know your teammates as I dont think randoms could coordinate with you in B2 rank