User blog comment:Kuopiofi/Saitama - Absolute or Supernatural?/@comment-25893909-20160906164927/@comment-24053170-20160907201224

Actually the plot of One Punch Man only states that Saitama can defeat his opponents in one punch(which has already been proven false, regardless of whether saitama held back or not in his fights against Boros and Garou, he didn't actually defeat them in one punch)

Also the author never said anything about Saitama not being able to be beaten.

Take Kenichi the Mightiest Disciple for example, the character of Hayato Furinji is basically invincible and can defeat any opponent only using 0.02% of his strength, and yet at the end of the manga Kenichi may or may not have beaten him in combat (its left ambiguous as to if he actually did since the author never actually confirmed it).

The author of One Punch Man could do the same by having Saitama be beaten offscreen. Besides a story about a guy who always wins every fight he is in eventually becomes meaningless and people would lose interest in it. So there is going to come a time in the story where saitama will in fact be beaten, in fact its pretty much a certainty at this point.

Though It may not come until later in the story, it will still eventually happen.

Also saitama's so called heat immunity isn't really well defined, as the heat he has experienced so far is nothing compared to things that are truly hot(atmospheric re-entry is only a couple thousand degrees, and genos blast of flame isn't really that hot either). When Saitama manages to walk away from getting struck by actual lightning (which is hotter then the surface of the sun) or withstands a stellar explosion/supernova or coronal mass ejection then he can say he is truly immune to heat.

Until that happens he is not truly immune to heat or fire and saying that he is is nothing more then a lie.

have a nice day.