Does THC kills sperm cells

not at all. You constantly regain millions of sperm per minute so this is something you shouldn't even worry about

Although the sperm will not be killed their by THC use, their swimming patterns will be disturbed by the effects of the toxic THC chemical. They

(the sperm) have been proven to swim too fast too soon to impregnate human egg cells in laboratory tests. Of course their are exceptions to any rule and those with existing sperm deficiencies may experience boosts in sperm cell production and fertility. Sperm require a burst of speed near the egg cell to effectively fertilize an egg cell. Sperm effected by THC use their speed burst too soon and too far away from the egg cell to effectively fertilize human egg cells in most tests. However individuals already stricken by sperm deficiency may experience opposite results as their sperm will gain the necessary burst required to fertilize the egg cell.