Who is Blast? And how strong is he?
Based on the amount of details given about his character, we can only speculate. Who is Blast? What are his powers? And how does he compare to Saitama in terms of strength?
To start off, we dont know much about blast, other than the fact that he is the top ranked S class hero. We also know that he can one punch enemies, just like Saitama. However to uncover the real details, we must dig a little deeper, that is to say, into the webcomic. We know that the hero association can misrank heroes sometime, because Saitama is C Class and King is S class. However, we also know that they do gauge heroes correctly because Tatsumaki is correctly ranked at the 2nd position in the highest class. This can only mean that Blast is also correctly ranked at the top which would in turn mean that Blast is not only stronger than Tatsumaki but also stronger than all the rest of the S class heroes.
We know that, from their fight in the webcomic, Tatsumaki can not overpower Saitama, as she was only able to lift him up even using her full efforts. Judging from this we can deduce that Saitama is powerful than Tatsumaki. But since we have not seen Blast fight or interact with anyone we cannot gauge him in comparison to Saitama. However that is where the real connection between Blast and Tatsumaki comes up. We find out that blast is the reason Tatsumaki became a hero. It leads back to events that took place 18 years prior to the current time, when Tatsumaki was imprisoned as a child and used for experiments because of her psychic powers. But to escape testing and possibly torture, she lies to her captors about her powers not working. One day, a chimera escapes captivity in the prison and Blast shows up to save the day and kills it.
This is where he tells Tastumaki to never expect anyone to come up and save her and she should become strong enough to fight for herself. This speech by blast motivated Tatsumaki to become a hero, similar to how Saitama has given speeches to characters such as king. Now aesthetic wise Blast has an appearance very similar to Saitama with both of their hero costumes consisting of a full body suit and a cape. This fuels some fan theories surmising that Blast’s true identity is Saitama himself. However we cannot put a rest to these rumors due to insufficient evidence.
Other than this we know that the reason he is absent from most, if not all, S Class meetings is because he is preoccupied doing more important hero work for the Hero Association. As far as we know Blast is also the first human to ever become a hero. As for rumors inside the universe, child emperor speculates that the strength of all the S Class heroes combined would not be able to math blast’s. Also, in a conversation with Saitama, Fubuki says that Blast rules over psychic power and billions of robotic forces and can even shoot lasers out of his eyes. Fubuki’s rumor may very well be true as Blast was able to tell that Tatsumaki was lying about not being able to use her powers providing some evidence that he may very well have psychic abilities of his own.
There are a multitude of fan theories out there but all we can really do is speculate about the true abilities and identity of Blast.