There are a few things that can make a leverage hackamore harsh: the length of the shanks, the noseband, and the positioning on the nose. The longer the shanks the more the pressure of the reins is multiplied. A wider noseband is going to be gentler, while a thinner one will be harsher. There are a lot of different nosebands out there- leather, plastic-covered chain, stiff rope, etc. The lower the noseband is placed on the horse's face, the harsher it can be because it's sitting on a more sensitive part.