User blog comment:Kuopiofi/Saitama - Absolute or Supernatural?/@comment-24053170-20160907020749

One other very notable weakness of saitama's is that for all his power and strength, he is still completely human and that he can and will die someday (whether by age, disease/sickness, poison, or something else). In fact anyone who could accelerate his age or induce death instantly would be able to defeat him without much effort.