Marvel: Organic Iron Manipulation

Lorna Dane (Polaris)
Polaris has such control over her powers that she is able to manipulate the natural iron within the blood of living organisms. She was capable of reversing the flow of an entire crowd's blood in order to render them unconscious.

Max Eisenhardt/Erik Lehnsherr (Magneto)
Magneto can control the traces of iron within organic matter and can manipulate the iron-enriched blood-flow to one's brain to potentially induce very limited effects. There are only 2.5 grams of iron in the bloodstream of a healthy human body and perhaps a gram at most in the rest of the body. As a reference, a penny weighs 2.5 grams. Magneto has used his magnetic abilities to extract the adamantium bonded to Wolverine's skeletal structure.

Onslaught
Onslaught can control the iron within any organic matter which allows him to have full control over an opponent's body. Onslaught has also demonstrated the ability to control the blood flow within one's body thus causing them to die a painful or even quick death.