Acid Sweat

Masaru Bakugo carries Acid Sweat, written 酸化汗 and read Sanka Kan. It is classed as an Emitter Quirk that operates on contact.

What it produces is sweat from the palms that is acidic and combustible at once, which leaves an otherwise mild man walking around with an explosive substance on his hands.

The fluid emerges from the palms the way ordinary perspiration does, and that is the crucial restriction: Masaru has no way to force it out on demand. Once enough has gathered, rubbing his hands together sets off explosions.

Chemically the description points toward nitric acid, going by what nitroglycerin is composed of, though the series stops short of confirming it and the match is a matter of inference rather than statement.

Masaru is the sole wielder, and the Quirk matters most through what it passed down. Combined with the Glycerin Quirk of his wife Mitsuki Bakugo, it produced Explosion in their son Katsuki Bakugo, which is why the boy has to secrete sweat before detonating and why his blasts grow with how much of it he puts out.

Mina Ashido's Acid invites comparison, but the two split on both counts. Masaru's comes out gradually, as sweat does, rather than in the quantities she can release at once, and hers carries no capacity to ignite.