The source material also suggests that Deadpool suffers from mental disorders as a side-effect of his extreme healing abilities. These include: attention deficit hyperactive disorder, manic-depressive disorder and onset schizophrenia.
Throughout the entire movie, it is said that he frequently displays many different psychological disorders including attention deficit hyperactive disorder, manic depression disorder, and schizophrenia. One of the disorders Deadpool is diagnosed with is severe ADHD, also known as attention deficit hyperactive disorder.
Deadpool is a mutant who has an accelerated healing factor. He can re-grow his parts or attach them if cut from his body. He is said to have cancer, which resulted in a deformed face, but he does not die due to his heavy healing factor.
Deadpool has constantly battled his fractured psyche throughout his comic book existence. It turns out that while his regenerative healing factor does protect against physical injury, it also greatly damages his mental health, resulting in severe psychosis.
Finally one student asked, “Is that what Deadpool has?” While being a fictional comic book character, I explained that Deadpool has what is considered multiple personality disorder, a real, yet rare disorder.
In the comics from which the movie is adapted, Deadpool is pansexual – he makes no distinction between genders or gender identity in his choice of partners. The term “bisexual” would be too narrow for Deadpool, who has flirted with Thor, propositioned Spider-Man and wouldn't rule out, say, unicorns.
One thing the MCU has done well is developing characters who struggle with mental health disorders. Though the process of diagnostics is quite complex, audiences can see how Thor struggles with depression or that Tony and Bucky Barnes have PTSD.
Deadpool, who now has almost unlimited powers from other mutants, is woken up to fight Logan. His mouth has been sewn shut so he can't talk, and his brain is controlled by Stryker. And he has Adamantium swords that come out of his hands.
Deadpool's immortality only extends to his ability to regenerate from almost any injury. However, this doesn't mean he's immune to everything. He can still feel pain, he can still be incapacitated, and he can still suffer from mental and emotional trauma.
This question is answered by the fact that Deadpool's cancer hasn't actually been cured but simply put on pause, meaning it is constantly battling with his healing factor, causing his severe disfigurement, which will assumedly still be in place when Deadpool joins the MCU in Phase 5.
Deadpool has bovinophobia, which is the fear of cows. According to him, cows "scare the *#$% outta" him, as he believes their stare to be chilling, like they're "waiting."
Deadpool's body is highly resistant to most drugs and toxins, due to his accelerated healing factor. For example, it is extremely difficult for him to become intoxicated. He can be affected by certain drugs, such as tranquilizers if he is exposed to a large enough dosage.
Deadpool became the Merc Without A Mouth after having it sewn shut so the writers weren't forced to derail their movie on his account.
Tony Stark is one of the regular humans. He's a genius, and is the MCU version of Elon Musk in wealth, which combined led to his Iron Man suit that makes him a legitimate superhero. However, in the words of Tony Stark: The Iron Man suit is just a result of Tony Stark's real superpower: ADHD.
Iron Man/Tony Stark
He needs a souped-up “Alexa” to function, and he still needs his personal assistant, Pepper Potts to keep him grounded because he can't even remember his own social security number. He makes up nicknames for everyone because people with ADHD often have issues with remembering names.
In the movie, it's because Wade was born with mutant genes, so every cell in his body would inherit regenerative powers – including tumor cells. The explanation is similar for comics: a mutagenic serum wouldn't distinguish between normal and abnormal tissues. Deadpool would have regenerating, superpowered cancer.
As some other answers point out Deadpool was able to survive for eight-hundred years in a room with no food or water.
Wolvie and Deadpool neither die nor can get older if they retains own healing factor. Hence they both ARE immortal.
Disease Immunity: The unique regenerative qualities of Deadpool's healing factor also extend to his immune system; he is immune to all diseases, infections, disorders, imperfection, and resistant to elemental extremes.
Deadpool has been through a lot, both as a hero and a villain, but if anything, he sees Wolverine as what he can be and what he should be. Logan is the measuring stick and if Wade is able to get that gruff government experiment to respect him and see the good in him, then Deadpool knows he's doing the right thing.
The key to these helpful additions to his power, all stem from the fact that Deadpool is constantly healing. This means that the neurons in his brain regenerate as they are perishing, causing him to think and react much faster and making him immune to brain injuries.
Borderline Personality Disorder. On the surface, Loki may appear confident, self-assured, and composed. Spend enough time with him, and we'd see what Thor sees. Loki's mood swings, recklessness, and impulsivity make him difficult to be around.
Thanos: Sociopath with a Heart
“Megalomaniac” fits well here. The second is characterized by repeated law-breaking, aggressiveness, and lack of remorse.