This is somewhat like asking how exposure to sun affects human life. It is good when it comes to converting provitamin D3, but bad when it causes skin cancer. Your question is very general, and the answer to it is similarly complex.
Many mutations have zero effect on human life, which is to say they are neutral. This is either because they are in non-coding parts of the genome, or they are synonymous mutations. Some mutations are beneficial. For example, a mutation in CCR5 receptor prevents human immunodeficiency virus (HIV) from attaching to cells, and makes those individuals resistant to HIV. Some mutations are bad most of the time, but beneficial under certain conditions. Sickle cell disease is not good in general, but protects against malaria. Some mutations are clearly bad, either because they significantly shorten the lifespan or degrade the quality of life - often both. Finally, an unknown number of mutations (it is likely large) cause death before birth, and we will most likely never know what they are.
For 8 genetic mutations that can give you "superpowers" see here.