There is no denying that She-Hulk is a powerhouse of a hero - strong, smart, and a capable martial artist - but does that put her on the same level as the mighty Thor? One shocking moment answered this question, with one of Marvel's ultra-strong heroes proving forever that they're in a different league to the other.
Jennifer Walters is an attorney who received a blood transfusion from her cousin, Bruce Banner. Getting a donation of the Hulk’s blood turned her into one of the strongest beings in Marvel Comics. She has been an Avenger, a Hero for Hire, a member of the Fantastic Four, and more. And unlike Bruce, she retains her personality and intelligence while transformed. This allows her to be more tactical with her strength and speed, and lets her use hand-to-hand combat skills learned directly from Captain America.
In What If? Civil War #1's 'What If Captain America Led All the Heroes Against Registration?' - from Kevin Grevioux and Gustavo Duarte - the Watcher reveals what would have happened if all the heroes of Marvel stood against the Superhuman Registration Act following Iron Man's death. This version of events sees Henry Gyrich unleash a whole army of obedient Thor clones against Captain America's Anti-Registration forces, leading to a slaughter. During the confrontation, heroes like the Thing and Carol Danvers are downed by lightning, while She-Hulk has her neck snapped by a single clone, showing that her regular form is no match for even a knock-off version of the God of Thunder.
The Thor clones are based off of Tony Stark's greatest mistake during the first Civil War event in the main continuity. Tony's Thor clone (dubbed Ragnarok) proved to be a near-unstoppable powerhouse. According to Captain America in the What If? issue, Thor only uses a third of his strength in battles against mortals. That means even if the clones only have a fraction of his true power, it still makes them insanely strong, and clearly strong enough to outmatch Jennifer Walters (at least without her recent Celestial upgrade.)
The Thunder God and Bruce Banner's Hulk have duked it out over the years, with various results. Unfortunately, Jennifer's control over her powers stops her accessing the same might as Bruce's raging behemoth. By her own admittance, her power is a fraction of Hulk’s - in World War Hulk #1, she even says that her cousin smashes “a thousand times harder” than herself. That is seemingly confirmed in this What If? storyline. Meanwhile, the original Ragnarok could only be stopped by Hercules, a hero who has beaten both Hulk and Thor.
Jennifer Walters is one of the strongest beings in the Marvel Universe, but even she was little more than an inconvenience for a clone of the Odinson. Though the story takes place outside main continuity, there is no reason to doubt the results, given this is not an alternate reality, but the outcome had events in the mainstream gone differently. While fans love to speculate which superhumanly-strong combatants would win a fair fight, when it comes to She-Hulk and Thor, Marvel already gave the definitive answer.