Blowbacks in King of Fighters are an important mechanic that can define certain matchups. The ability to retaliate on block is powerful, and as such the techniques to deal with them are vital to playing the game at higher levels. YouTuber sigmaG19 put together this useful tech video showcasing ways to deal with blowbacks with several different characters, as well as ways that this technique was handled in past games.
There is also a great video by Gato Ray on blowbacks, covering options for nearly every character to punish blowbacks on block.
He even provided a helpful “blowback tier” chart describing how difficult to punish each character’s blowback is, and can be found here. For the most difficult to punish characters, he made this follow-up video featuring several punishes capable of reaching the opponent.