- "I wanted to be a superhero. Always wanted a real super suit."
"When was the last time you saw a plus-sized superhero? Never. The industry discriminates."
- ―Firefist and Deadpool
Firefist (born Russell Collins) is a mutant with the ability to generate and control fire. While using his powers, he instinctively generated a super-thin, invisible psionic energy field around himself that protected him from heat and flame.
Due to Alkali-Transigen putting mutant-suppressing chemicals in the products used in mass food production, Russell is one of the last natural born mutants.
Russell grew up in the Essex House for Mutant Rehabilitation where he was tortured by the headmaster of the orphanage simply for being a mutant. This sparks the anger in him, causing him to want revenge. Eventually, Russell snaps and lets loose with his pyrokinetic powers. The X-Men – Colossus, Deadpool, and Negasonic Teenage Warhead – arrive to stop him. Deadpool managed to talk him down but realizes that the staff at the orphanage have been abusing him and kills a member of the staff. Both mutants are arrested, placed in power-dampening collars and taken to the Ice Box prison.
Russell manages to sneak in a pen in his butt that he plans to turn into a shiv. His plan in prison is to find the largest guy in prison and start a fight to earn respect. Deadpool tries to get him to see the reality of prison, but Russell believes that he and Deadpool are a team that will protect each other. Unfortunately, Deadpool's collar stops his healing power, meaning his cancer returns. Deadpool is sure he is going to die in prison and not be useful in protecting Russell so he tries to make him see how his plan is not going to work. The Ice Box is attacked by Cable, a time-traveling mutant intent on killing Russell.
In the future where Cable comes from, Russell is a terrorist who, upon having his revenge on the headmaster, starts to enjoy killing people and commits mass murder throughout his life. In that particular timeline, he and Cable frequently clashed with one another, with the latter coming close to killing him a few times. Russell decided to hurt him by going after Cable's family. He broke into his home one night, and with Cable gone at that time, his wife and daughter were defenseless. Russell used his powers to set their home ablaze, killing Cable's family as a result. This, in turn, started Cable's mission in traveling to the past to kill Russell long before he killed his family.
During the attack on the prison, Deadpool's collar is knocked off and he manages to recover enough to fight Cable. Both Deadpool and Cable are thrown from the prison by a concussive blast. Left in the Ice Box, Russell ends up befriending the Juggernaut.
After the attack on the prison, all the Ice Box prisoner are due to be transported to another facility. During the trip, the transport is attacked by Cable, although Deadpool and Domino try to stop him. Russell manages to let himself out of his cell with his pen, then frees the Juggernaut who crashes the transport. Russell and the Juggernaut escape.
Intent on revenge, Russell, and Juggernaut head to the Essex House to kill the headmaster. Cable teams up with Deadpool and Domino to stop them, noting that this would be Russell's first kill which would set him on the path to the future that Cable is trying to avert. Deadpool tries to stop Russell by convincing him that people care for him by placing a power-dampening collar on himself and offering his life in place of the headmaster. He even takes a bullet to the heart from Cable, who was not convinced that Russell could be stopped. The sacrifice stops Russell and makes him lose his thirst for revenge upon seeing Wade die to protect him. Seeing this, Cable travels back in time to ensure that Deadpool did not die from his bullet by hiding a skee-ball token into Wilson's costume, which ends up blocking the bullet. Russell is still saved and the dark future is averted, with Cable's family alive.
The Westchester Incident
In 2028, Charles Xavier developed Alzheimer's and suffered a massive seizure that injured 600 people, and killed 7 mutants, including several members of the X-Men. It is unknown if Russell was among those who were either killed or injured.
Russell is an angry, hot-tempered, foul-mouthed boy. This all stems from the abuse and torment from the staff at the orphanage he was sent to. Despite this Russell is still a good kid and is willing to stick up for those that he considers friends. After seeing Deadpool take a bullet for him and die to protect him, Russell changes and doesn't become the monster that destroyed Cable's timeline. Cable forgave him and rewinds time to save Wade from the bullet.
- Pyrogenesis - Russell has the ability to generate fire from his hands.
- Pyrokinesis - Russell possesses powerful pyrokinetic abilities,able to emit powerful flame blast. He can create flames around his body or up to twenty feet away from himself.
- Fire and Heat Immunity - While using his powers, he instinctively generated a super-thin, invisible psionic energy field around himself that protected him from heat and flame, but not from other forms of injury.
- Russell shares his name and abilities with Marvel Comics character Russell "Rusty" Collins.
- According to Deadpool, Russel is 14 years old in Deadpool 2.
- Both Russell and Mystique had men travel from the future to try and stop them from making their first kill.
- Julian Dennison felt the role of Firefist was particularly special because his character is "chubby". He said in an interview: "...playing a chubby or fat superhero was so special because I would go and watch these movies with my friends and would never see anyone like me. I am excited to be that for other kids who look like me."