Susan Storm aka the Invisible Woman is not only one of most beautiful women in Marvel Comics, she's also one of the most powerful. As a member of the Fantastic Four, she has proved herself against some of the greatest foes in the Marvel universe while also juggling responsibilities as a wife, mother, and philanthropist in her unorthodox superhero family. Sometimes she has to make tough choices regardless of the consequences to save the day - something her Ultimate Marvel counterpart knows all too well since a kiss from Susan Storm once saved all of New York City and its inhabitants from drowning in a Biblical flood.
In the Ultimate Marvel universe - a long-running alternate reality meant to introduce readers to a modern interpretation of Marvel characters unburdened by confusing continuity - the Fantastic Four helped Susan Storm's mother in her discovery of the lost continent of Atlantis. In the story "Tomb of Namor" by Mark Millar and Greg Land, which ran over Ultimate Fantastic Four #24-26, the Four's undersea exploration of the ancient advanced civilization uncovered an actual living survivor who had been entombed in a kind of cryogenic suspension. The survivor, an Atlantean being named Namor, briefly fought the young superheroes until he was knocked unconscious, later displaying extreme levels of intelligence, power, and arrogance. Showing an attraction to Susan Storm, Sue agreed to show their time-displaced guest around, even though the situation did not sit well with her teammates, especially her boyfriend Reed Richards.
When the situation with Namor turned sour after discovering he was actually an imprisoned criminal, the rest of the Fantastic Four showed up, ready to take him down. Namor's strength and powers made him more than a match for the Thing and the Human Torch, and Reed's superior mind only stopped him temporarily. With their combined might, they appeared to defeat Namor, telling him to surrender and that his actions were like those of a petulant teenager. Outraged and unable to accept defeat, Namor uses his powers to manipulate the nearby water. Summoning a vast water construct to submerge the city, the ancient criminal states that he will only relent if he receives a meaningful kiss from Susan - conditions that Susan agrees to, given the clear and present danger.
The relationship between the Fantastic Four and Namor in the mainstream universe has been tentative at best, with tensions between Reed Richards and the King of Atlantis over his admiration of Sue Storm. Although she's resisted his advances in the past, her Ultimate counterpart agrees to this, seeing it as a way to save everyone and get rid of the Atlantean annoyance at the same time. Reed is visibly surprised and distressed by Sue's choice (he has to be restrained by his teammates as Namor and Susan kiss), and the worst criminal in Atlantean history even manages to gloat about how passionate it was.
With Namor's request fulfilled, he returns to the ocean and life returns to normal, with Susan's relationship with Reed undisturbed as Mr. Fantastic later compliments her on her bravery in that moment. The Ultimate version of Namor would return occasionally to help Susan, his favorite among modern-day society, and he would clash with Reed again during the earth-shattering events of Ultimatum. The Invisible Woman saved New York City with a kiss - a feat the rest of the Fantastic Four have yet to equal.