Ever since Bruce Banner was first inundated with gamma rays and transformed into the Hulk, his monstrous alter ego has proclaimed himself "the strongest there is." It's a bold boast in a universe filled with Avengers, gods and cosmic titans, but the Green Goliath isn't one to shy away from the competition. No matter what the multiverse has thrown his way, the Hulk has always risen to the challenge.
Over the character's long and colorful history, readers have seen just about every variety of Hulk imaginable. There have been green, grey and red Hulks, a terrifying Immortal Hulk, and even a menacing future Hulk. Perhaps no incarnation was more infamously powerful than the Hulk's planet-shattering World-Breaker form, emerging at the end of the Planet Hulk storyline and featuring throughout World War Hulk. However, for a fleeting moment in 2011's "Heart of the Monster" storyline, the Green Goliath may have put even the World-Breaker to shame.
At the start of this 2011 story, which played out in Greg Pak and Paul Pelletier's Incredible Hulks #630-635, we find a Bruce Banner who is clearly not as over his ex-wife, Betty Ross (now the Red She-Hulk), as he claims. The news that she has run off with the Hulk's old enemy Tyrannus doesn't help matters, either. While the Hulk's allies -- She-Hulk, A-Bomb and Amadeus Cho -- worry about Bruce's well-being, Tyrannus brings Betty to his underground kingdom. Here, he invites her to drink from his Fountain of Youth, deeming her "a partner worthy of sharing [his] journey through eternity." But before they can complete the ritual, however, a team of AIM scientists invade the hidden lair and transform the Fountain of Youth into a wishing well. With that, the moral of this particular story quickly becomes apparent - be careful what you wish for. Any ambiguity in a wish could -- and does -- lead to horrific unintended repercussions.
When Amadeus asks for help while standing in the well, he unwittingly unleashes a plethora of the Hulk's greatest enemies. The ensuing battle leads to Hulk's World-Breaker persona being unleashed. Keeping him from destroying the continent, the sorceress Umar appears and ushers the Hulk to her realm - the Dark Dimension. It later emerges this journey is the product of Hulk's enemies wishing for him to be wiped from the face of the earth forever. The well has trapped Hulk in a dimension with neither death nor innocent lives. Without the need for restraint, Hulk's power can grow exponentially.
While the World-Breaker had always been unstoppably powerful, even in this form the Hulk had never reached the upper limit of his strength. Preparing for battle in the Dark Dimension, the Hulk admits to his allies that when he had previously taken on the World-Breaker form, he had always been holding back. This time would be different. The Hulk unleashes all-out war in the Dark Dimension, between himself, his enemies and the Red She-Hulk, the woman he has both loved and hated. The Hulk is at last so utterly freed from fear and restraint that his powers can soar beyond any level he has ever reached before. So absolute is the transformation that the Bruce Banner persona even starts to fade away, the surest sign that the Hulk has reached the zenith of his incredible strength, making him more fearsome than ever.
The Hulk seen here is the World-Breaker taken to a whole new level of power, among the strongest forms the Hulk has ever assumed. It perhaps peaks in the story's finale, when Hulk and Red She-Hulk are tricked back to Earth to confront a gamma-charged Fin Fang Foom. Absorbing the energy the dragon had stolen from an array of gamma bombs, both already-super-charged Hulks reach giant size. Only the realization he now poses a threat to the Earth -- and that his similarly gamma-irradiated allies need his help -- stops the Hulk. With the last of the wishing well's power, all the Hulks are returned to normal and given the power to control their transformations at will.
For the briefest moment, though, the power to destroy the entire planet lay at the Hulk's feet. The story's closing moments see Bruce musing on the incredible power he had wielded. And it ends with the chilling conclusion that the rage that produced such power couldn't be attributed to either the Hulk or Bruce Banner since the two are one and the same.