Are Nuclear weapons a good or a bad thing?

ultimately a bad thing because they're main objective is to kill millions of people. It leaves a huge ring of infected land through radiation so that nothnig can grow or live where a nuclear weapon went off. They could be good in one way. If people know that a country has nuclear weapons they are less likely to attack or bomb that country is fear of the other country respondign with a nuclear attack.

Ultimately bad...

If you examine the contaminated area around Chernobyl, the normal vegetation and wildlife grow and live quite well. They are doing much better than before the disaster as they are isolated from men.

Both Hiroshima and Nagasaki were repopulated and rebuilt within 5 years of the end of WW2.

Both examples prove you wrong.