So far, She-Hulk: Attorney at Law has given Marvel fans, who are always ravenous for familiar faces, plenty of reason to celebrate. The show has already seen appearances from many popular heroes, including the Sorcerer Supreme Wong, the titular superhero's cousin, Hulk himself, and a few folks that have not been seen in the MCU for quite some time: namely, Emil Blonsky, also known as Abomination.
The series has also introduced a handful of new yet equally compelling characters. Some of them have essentially been used as one-off jokes, like Madisynn, a tipsy twenty-something woman who found herself imbued with portal powers after a run-in with hack Vegas magician and Kamar-Taj reject Donny Blaze, or shape-shifting Asgardian Light Elf Runa, who convinced a misogynistic lawyer that she was musical phenom Megan Thee Stallion. Others, like the series' primary antagonist Titania, are featured more heavily and have quickly cemented themselves as classic MCU characters.
In the most recent episode of the series, "Just Jen," a new superpowered individual was introduced. Though he is presented as a feckless philanderer, he may have one of the most extraordinary abilities in the entire MCU canon. The Avengers had better hope that this regenerative rapscallion never expands his villainous pursuits beyond the mistreatment of his romantic partners.
Who Is Mr. Immortal in the Broader Marvel Universe?
In Marvel Comics, Mr. Immortal, or Craig Hollis, has his hand in several prominent organizations. He is one of the founding members of the Great Lakes Avengers, a spinoff team of the famous superhero collective that is based in the Midwest. Later, when the members of the GLA discover that they are all mutants, the team decides to rebrand themselves as the Great Lakes X-Men.
As his superhero moniker suggests, Craig Hollis is immortal. Every time he dies, he regenerates. Given his inability to pass on, it's easy to understand why the character is such a tragic figure. He is forced to watch helplessly as generations of his loved ones die, and his heroics are all forgotten in the fullness of time. This includes his primary romantic interest, Dinah Soar, a pink reptilian extraterrestrial who dies while fighting supervillain Maelstrom with the Great Lakes Avengers.
Mr. Immortal's Laundry List of Former Partners
However, in She-Hulk: Attorney at Law, Mr. Immortal bears little resemblance to the comic book iteration of the character. He does have the same regenerative capabilities; when his pair of attorneys begin to raise their voices, he leaps through a nearby window, obliterating the car he lands on, before hopping up to his feet, frazzled but unharmed. However, instead of being portrayed as a heroic figure, the version of Craig Hollis in She-Hulk is a commitment-phobic scuzzball who uses his immortality to fake his own death and escape from relationships. When all his former alter egos are made public knowledge on the mysterious website Intelligencia, these scorned individuals demand a settlement.
Mr. Immortal has been accruing jilted lovers for years, and many of his currently living former partners file a suit against him. The women (and one man) who attend the meeting seemingly come from all walks of life. Hollis even mentions that his first wife was Baroness Cromwell, a vampire and fellow immortal from the Marvel comic books. His wives and husband want retribution for the time they spent together, as well as any financial hardships they endured due to Mr. Immortal's slew of commitment issues.
Mr. Immortal is a Difficult Challenge for GLK&H Attorneys 
The law firm GLK&H only recently expanded into the realm of superpower-centric litigation. When Jennifer Walters was hired, her first assignment was the defense of Abomination, Emil Blonsky's monstrous, gamma radiation-induced alter ego. However, Craig Hollis's long history of mistreating his partners necessitated a creative strategy from his legal team.
When his former partners begin to argue, Mr. Immortal seems ready to start the cycle of regeneration once again. Still, his lawyers ultimately settle with the spouses by divvying up the wealth he had amassed over his unnaturally long life. Hollis is unfazed by losing his fortune, but one of his lawyers, Mallory Book, also includes in the settlement that Mr. Immortal must offer his former partners a sincere apology, coupled with sustained eye contact.
There have already been so many fascinating characters featured in She-Hulk: Attorney at Law, and there will likely be more cameos to come. Mr. Immortal seemed like a one-off, but his abilities would undoubtedly be useful to any hero or villain organization if he were. If a future episode features all of the superpowered individuals who lost suits against GLK&H teaming up, Mr. Immortal will be a tough nut to crack, even for She-Hulk's powerful fists.