The Hulk is one of the most powerful beings in the universe since his powers increase with his rage, because of that he is capable of matching the power of beings like Thor and Silver Surfer.
The process by which Banner usually transforms into the Hulk is presumably the result of the chemical catalyst, adrenaline (a.k.a. epinephrine). As in normal human beings, Banner's adrenal medulla secretes large amounts of adrenaline in time of fear, rage, or stress, which hormonally stimulates the heart rate, increases blood-sugar levels, and inhibits sensations of fatigue. Whereas the secretion heightens normal physical abilities in normal human beings, in Banner's case it triggers the complex chemical-extra-physical process that transforms him into the Hulk. The total time of transformation falls anywhere between seconds to 5 minutes, depending on the initial adrenalin surge, which will be determined by the original stimulus. Soon after the transformation, the amount of adrenalin in the Hulk will return to more normal, reduced levels. However, there were instances in which Banner became the Hulk without any discernible increase in heart rate or adrenal levels, suggesting that the true trigger mechanism into the Hulk is far more psychological than physical. When the Hulk transforms back into Banner, the excess muscle mass and energy is lost, presumably to the same place he derives it.
The Hulk possesses the capacity for vast levels of physical strength. The Beyonder once stated that the Hulk's potential strength is limitless . His strength has been additionally described as limitless. However, each of the core Hulk personalities possesses a base strength level. While in a functionally calm state, the Gray Hulk is able of lifting 70 tons, the Savage Hulk can lift 90 tons, and the Professor Hulk can lift about 100 tons. The incarnation sometimes referred to as "Green Scar" is the physically strongest of the primary Hulk incarnations. After being exposed to energies from the exploding core of the ship that brought him to Sakaar, his base strength level was dramatically increased. While in a "calm" state, the Hulk was able of lifting well over 100 tons. However, while he is in an enraged state, adrenaline surges through the Hulk's body, what increases his strength considerably beyond his base limits. Among his amazing feats are supporting a 150 billion ton mountain, overpowering bunker designed to withstand an explosion several thousand megatons in magnitude, knocking out the Human Torch, the Thing and the Invisible Woman, in a classic battle against them , destroying Crypto Man after he was boasted with strength superior than Thor's , overpowering Thor fighting against the Wonder Man, the Iron Man, the Vision and the Scarlet Witch, while narration states that Hulk's power is even greater than their combined might fighting against the West Coast and East Coast Avengers teams during a prolonged period of time despite of being very weakened due to separation from Bruce Banner, almost breaking the East Coast and threating to break the whole planet by the mere output of force from all his body, with the awesome energy becoming work, overcoming a power-depleting machine which contained much of the combined power of himself, the Silver Surfer, the Doctor Strange and Namor , smashing pure adamantium , holding together the entire space-time structure to impede the Defenders of being sucked into a fissure , holding together the tectonic plates of a planet, overcoming a field of pure energy powerful enough to change the orbit of a planet, pushing two enormous spheres of matter and antimatter apart, destroying an asteroid twice the size of Earth due especially to his toughness and, according to Newton's Third Law, to the impulse generated by the contraction of his legs, breaking up the own space-time barrier , cracking the Onslaught's armor, who was at least Celestial level in power, ripping out a device designed to fight against the Celestials, sending concussive force throughout countless dimensions due mostly to his power. The Mighty Thor cited that the Hulk may be stronger. The Hulk also grows even stronger the more radiation and the more dark magic he absorbs.
The Hulk can survive on very little sustenance, but after the Hulk adapts to a hostile environment (like space) he no longer needs sustenance and does not need air, water, food, or sleep.
The Hulk ages at an incredibly slow rate. Because of his great healing factor that regenerates his cells, and the gamma energy and the dark magic he has absorbed that empowers him, the Hulk has an extremely long lifespan. A possible alternate persona, the Maestro, was still in his physical prime despite being more than one hundred years old . In another alternate future the Hulk outlived mankind on earth and was still in his physical prime .
Regardless of his size, Hulk's superhumanly strong legs allow him to run at speeds that are far beyond the natural physical limits of even the finest human athlete (about 770 mph). Nevertheless, this does not grant him any enhanced reflexes or agility as smaller foes exploit his size and use it to their advantage. However, he has been fast enough to catch mortar shells shot at him.
The Hulk's body counteracts fatigue poisons that build up in his muscles during physical activity. In an enraged state, he is capable of exerting himself at peak physical capacity for several days before fatigue begins to affect him. However, much like his physical strength, the Hulk's stamina does increase as he becomes angrier.
In addition to great strength, the Hulk's body possesses a high degree of resistance to injury. The Hulk's skin is impervious to conventional blades, adamantium and vibranium being amongst the very few metals that are truly capable of piercing his skin. The Hulk is capable of withstanding high caliber bullets, powerful explosives, pressures extremes, falls from orbital heights , maximized heat without blistering, maximized cold without freezing, and great impacts. The Hulk has withstood the impact of a ground zero nuclear explosion and also the Human Torch's Nova Blast , with a temperature of one milion degrees Fahrenheit, without any injury. The Hulk was also able to withstand the force equivalent to thousands of nuclear weapons , planet-devastating impacts at point blank, and a powerful blast from Galactus. The Hulk's durability, like his strength, is fueled by rushes of adrenaline while angry.
Regenerative Healing Factor
Despite his high resistance to physical harm, it is possible to cause the Hulk injury. However, he is capable of regenerating damaged or destroyed areas of his body with far greater speed and efficiency than an ordinary human. For example, during a battle with Vector all of the skin and much of the muscle mass of the Hulk were destroyed. It took the Hulk moments to regain the mass and be completely healed. The Hulk's healing factor enables him to recover from any physical transmutation. He also heals faster and more efficiently the madder he gets.
Resistance to Psychic Control
In many instances, the Hulk has demonstrated great psychic resistance as a side-effect of his rage and the multiple personalities inside his mind.
Immunity to All Diseases and Viruses
The Hulk is immune to all known Earth-based diseases and viruses, including AIDS . He can operate under intense conditions for extended periods of time due to his body not developing fatigue toxins quickly.
Superhuman Leaping Ability
The Hulk is able to use his highly developed leg muscles to leap great distances. While calm, he is capable of leaping roughly 3 miles. However, as he becomes enraged, his strength increases considerably, which means he can jump much farther than usual. On more than one occasion, the Hulk has nearly jumped into orbit. The Hulk has also been known to cover 1,000 miles with a single leap. Other example of his leaping ability is shown when Hulk jumped on top of Mount Olympus from ground level, in a single leap . The Hulk also shows incredible precision with his ability to aim his jumps and landings. He has grabbed missiles of the air on multiple occasions and landed on tiny islands that were barely visible from the height he fell from.
Adaptation to Hostile Environments
There have been several instances in the past where Hulk has not only spent extended periods of time in oxygen-less outer space without suffocating, but he has also moved his mouth and spoken in these environments. The Hulk's body is capable to adapt itself to new inhospitable environments whenever it is necessary. Like his healing factor, it is believed that this ability is also fueled by his rage and the madder the Hulk is, the quicker the Hulk's body will adapt.
The Hulk has been seen on the ocean floor a number of times so that he is capable to breathe due to his body developing a gland which creates an oxygenated perfluorocarbon emulsion which fills his lungs and equalizes the pressure. He is therefore able to breathe fluid and avoid decompression and nitrogen narcosis.
Astral Form Perception
The Hulk has the unique ability of being able to see "astral forms"--or ghosts . This power has come in handy when working with his fellow Defender, Dr. Strange, who is able to leave his body in an usually invisible, ghost-like state better known as an astral form. Banner subconsciously feared his father's ghost would come back to haunt him, and so the Hulk developed this mechanism to allow him to look out for him. More recent events have shown that the power to see astral forms may now extend to Bruce Banner. However, it was suggested the clarity of the astral forms is diminished when compared to the Hulk's ability to view them. The Hulk's ability to see astral forms may go beyond just seeing individual spirits. The Hulk once experienced a whole town in the middle of the desert that faded away into nothing. While it is possible it was merely a mirage, the issue suggests it is possible the Hulk was able to see a town that didn't exist in our plane of reality that no one else could see.
The Hulk also has a seemingly mystical homing ability that enables him to locate the area in New Mexico where he first became the Hulk. This applies even if the Hulk is in another dimension. An image of the Maestro once explained to Bruce that the reason he was able to do that was because the Maestro's spirit was there, calling to him. However, since the time Maestro was resurrected the Hulk has continued to return to the gamma bomb site, suggesting that there is more to his ability than merely the Maestro's spirit. This homing ability has also been used to find people on rare occasions. For example, the Hulk was able to dig a tunnel underground exactly in the direction of the Onslaught. While it is possible that Onslaught was mentally leading the Hulk to him, there were other instances of Hulk demonstrating this ability. The Hulk's instincts led him to Rick Jones and Betty and the Hulk located the Abomination with no prior knowledge of his whereabouts.
Gamma Radiation/Energy Manipulation and Emission
Not usually a power associated with the Hulk, but there is enough evidence that Hulk possesses at least a limited ability to manipulate forms of energy, particularly gamma radiation. The Hulk's body works like a "gamma battery" by creating and radiating gamma energy. Armageddon once wanted to use Hulk's own energy to power machines capable of bringing his son back to life. However, the Hulk outsmarted him by consciously force feeding his own energy into the machines at a rate too fast for them to handle and they promptly overloaded and exploded. He also generated massive amounts of gamma energy during World War Hulk. The extent to which Hulk controls his own energy, and foreign sources of energy, is yet to be determined.