Question

why making an anti viral medicine is difficult than making an anti bacterial medicine

Answer 1

This is because anti bacterial medicines block the formation of cell wall of the bacteria. When, bacterias don't have cell wall, they don't divide and hence they die. While, viruses don't have their machinery of own. When they enter into our body, they use our cells as their machinery. So, to kill viruses we've to kill some of our cells as well.
Hence, making anti-viral drugs is more difficult than making anti-bacterial drugs.