The Molecule Man (Owen Reece) has the ability to mentally manipulate molecules, allowing for a variety of effects, such as the creation of force fields, energy beams and hyperspace portals. It doesn't sound like a particularly powerful set of abilities in the grand scheme of things and that, added on to the fact that he has a very modest, human appearance, means he is often vastly under-estimated as a villain in the comic book fan community. However, the fact is, he is one of the most powerful characters to have ever existed in Marvel comics. He gained his powers when, whilst working as a lowly laboratory technician at a nuclear plant owned by the Acme Atomics Corporation, he accidentally activated an experimental particle generator, which bombarded him with an unknown form of radiation. The radiation had a mutagenic effect on Reece, releasing his potential for psionic powers on a cosmic scale. He could now control all types of matter, even down to the molecular level, and all types of energy. The accident also left markings resembling lightning bolts across his face. The following day he was sacked for his carelessness. He then named himself the "Molecule Man" and became a villain, taking vengeance on a world which had previously left him feeling bitter, anonymous and unloved. His power is such that he has been able to completely destroy objects as powerful as Thor's hammer Mjolnir, Captain America's vibranium shield, Iron Man's armour and the Silver Surfer's supposedly indestructible board (see picture above). He has also been able to regenerate his entire body, after it was destroyed, from the genetic imprint left by his fingers on his wand (a rod he used to focus his powers through). Essentially, he's massively powerful and nearly unkillable - certainly nobody in the current MCU is capable of defeating him at his most powerful. That said, he hasn't always been a villain and his power has depleted somewhat following a retcon, but if he was to be introduced on screen as he was in the comics, he'd undoubtedly be a threat to the entire MCU.