Will chopping hard destroy my new knives? I bought a new set of knives and my dad used the chopping knives to cut onions. 

Instead of chopping by slicing the onions with the usual technique, he was using his two hands to hold the knife by the extremities and chopping the onions this way. Is this going to destroy my knives?
Hard chopping will not destroy the knife, but it will dull the knife faster. The edge of a knife is extremely narrow. As a result, regular use will push the edge to the left or right, leading to burrs. Hard impacts accelerate this process, and can even cause the edge of the blade to chip. Knife blades stay sharp longest when they are used gently and on soft cutting surfaces.