ALTERNATE VERSIONS
In the year 2013 of the dark future called Days of Future Past, Sentinels ruled America. Mutants were either killed or locked up in concentration camps. Piotr Rasputin was married to Kate Pryde and they had a few children, who had been killed by the Sentinels. The remaining X-Men came up with a plan to change their timeline, and had Rachel Summers briefly exchange Kate’s mind with that of her past self, to warn them of a crucial event that caused the dystopic future they lived in. While Kate was on her chronal journey, the other X-Men attacked the main Sentinel base in a suicide run. By the time his wife returned, only to find that nothing had changed, for she had accidentally traveled to the past of an alternate timeline, Colossus was already dead.
In the Age of Apocalypse, Peter Rasputin was one of Magneto's original recruits and served a series of long and distinguished stints with the X-Men. Here too, he and Shadowcat were married and eventually were placed in charge of training Generation Next, the new wave of young mutants being primed to become X-Men. Colossus was a very haunted figure in the AoA 
and had suffered his share of tragedies. His sister, Illyana, was apparently killed years earlier, and his older brother, Mikhail, had betrayed humanity to serve as one of Apocalypse's Four Horsemen. Piotr's face had been scarred by acid, and not only did he constantly maintain his metal form, he also wore a mask to hide his deformity. A man on the brink of sanity to begin with, Rasputin was driven over the edge after the prize of being reunited with his sister, Illyana, was dangled before him. He selfishly abandoned his students to their deaths in the prison hellhole called The Core and, later, after learning that Illyana would cease to exist when the AoA was undone, he barreled his way through his fellow X-Men in an attempt to save her, injuring and possibly killing many of them, including his own wife. Piotr died but many years later he was resurrected by Dark Beast, who had use for him in the new regime. Apocalypse had died but Weapon X had risen to take over the world as Weapon Omega. Colossus was brainwashed and used as a bodyguard to the new leader but was freed from his service by Monet St. Croix. She used her telepathy to undo the brainwashing and bring him on to her side to oppose Weapon Omega’s rule.
Colossus’ history diverged at a much earlier point in the timeline shown in What if (2nd series) #110. Illyana Rasputin was run over by a tractor while Professor Xavier tried to recruit Piotr for the X-Men. Blaming Xavier for his sister’s death (as if he hadn’t been distracted him, Piotr might have saved her), he refused to join the X-Men, instead becoming a member of the Russian Supersoldiers. Colossus quickly became the leader and started a relationship with his teammate, Darkstar. Without Colossus, the X-Men fared badly against Proteus several months later, who managed to possess Phoenix. The Supersoldiers were called in to help and Xavier urged Colossus to assist him in saving Jean’s life. Xavier managed to persuade Proteus to use him as a host body instead of Phoenix, and Colossus then killed Xavier and Proteus, losing an arm in the process. Following the events of that day, Colossus retired and married Darkstar. Eventually, they had a daughter, whom they named Illyana.
In the Mutant X universe, Colossus suffered an even worse injury. During a battle between the X-Men and the Hellfire Club, Harry Leland used his control over gravity on Colossus, making him sink into the ground. Rogue grabbed him by the arm, but Selene cruelly dissolved Rogue’s gloves, her absorption power kicking in. Hesitating a bit too long while pondering the decision wether to let go of Piotr, meaning he would be buried alive, the X-Woman accidentally permanently absorbed his powers. Colossus was rendered comatose and never woke up again. His psyche in her head has been tormenting Rogue ever since.
Quite a large number of former super-heroes became leaders of the world’s nations in the Earth X reality, and the former Soviet Union was no exception. Colossus was now Tzar Piotr, ruler of all of Russia. Rasputin was an extremely powerful man, overseeing Russian's vast storages of grain, 
one of, if not THE, greatest food source left on Earth following the mutation of livestock and other animals into sentient Ani-Men. The Black Widow was always at Piotr's side as his top advisor, though apparently she was someone other than Natasha Romanoff. Also, the Piotr of this timeline discovered that he and Mister Sinister were one-and-the-same: apparently, Colossus would develop a mad love for Jean Grey and travel back in time for the sole purpose of preserving her as a clone. This concept was only mentioned in passing, however, and was not fully explained for posterity.
In the Ultimate universe, Peter Rasputin worked for the Russian Mob to feed his family, until he was recruited by the X-Men. After some time, he silently left the team dissatisfied, feeling they didn’t truly care about him and that being a mutant was useless. That changed when the X-Men asked him back and when he used his strength to save a sunken Russian submarine. Over his time with the X-Men, Colossus came to realize that he was gay and began a relationship with Northstar. Things did not go smoothly though, as the rest of the X-Men found out he was addicted to a drug, called Banshee, that enhanced a mutant’s natural gifts. When Northstar was kidnapped by Alpha Flight, Colossus coerced a group of X-Men to take the drug and rescue Northstar. Things went horribly wrong though, with Northstar becoming paralyzed in the rescue attempt, and the other Banshee-free X-Men showing up. In a drug-fueled craze, Colossus took on his own team but was stopped when his heart was ripped out by Wolverine. His life was saved but he was unable to shift back in to flesh form for a while.
After the Magneto’s Ultimatum wave hit and most of New York was destroyed, mutants were put into camps in a bid to contain them. Colossus ended up at Camp Angel and was brutally tortured by the guards there looking for information about Magneto’s crimes. When the news emerged that mutants were the product of genetic experiments, the inmates started to rise up. Both 
Storm and Stacy X led the charge against the human captors and they freed Colossus from his confinement. When they took over the camp, the two women were at odds on what to do with the guards they took hostage. Colossus ended up casting the deciding ballot in the vote and he chose to execute the guards, going as far as to crush one to death with his own hands. Colossus disappeared off the radar for a while and, in that time, a mutant cure had been released, with most mutants choosing to take it. Those who didn’t were allowed to live on a reservation called Utopia. Colossus made his way to Utopia just in time to aid them in a fight with a renegade group of mutants led by Jean Grey. The leader of Utopia, Kitty Pryde, decided to take the war to Jean and so she put Colossus in charge of the reservation whilst she was away.
A variation of Colossus was chosen by the mysterious Time Broker to aid Weapon X in their cross-dimensional missions. One can only wonder if the Broker had a crossed wire somewhere, for while the Exiles' Illyana Rasputin was far more brutal and self-serving than her teammates, the Piotr Rasputin of Weapon X lacked the killing instinct his fellow travelers employed almost constantly in carrying out their missions. Colossus came to his untimely end when he befriended a young Kitty Pryde on one mission, and opposed both the Tallus decree of slaughtering all remaining mutants on that Earth and the separate megalomaniacal plans of his teammate, Hyperion. Both Colossus and Pryde were blasted out into the void from Asteroid M, and died in the cold vacuum of space.
During the Battle of the Atom crossover, a future was depicted that showed what things would be like 25 years in the future if the time-displaced original X-Men stayed in the present day. The X-Men had been torn apart by many deaths and tragedies over the years but Colossus still remained a steadfast member of the team. Losing his sister some years before, 
he acquired her soulsword and wielded it like his own. When the present-day Magik teleported to the future, he was delighted to see her and immediately decided to help her with her problem. The future Brotherhood had travelled back in time to force the original time displaced X-Men to return to their own time, and so Colossus took a group of his own X-Men to confront them. Landing in his version of the past, he met up with the present-day X-Men to confront the future Brotherhood. During the final battle with the villains, Colossus had his mind destroyed by a future son of Xavier. There was no way to save him and his body was sent back to his own time to be buried in Russia.
On Battleworld, a domain existed that showed what might have happened if the X-Men lost 
Inferno. Magik was unable to be saved and so the part of New York that had merged with Limbo was magically sealed off. Colossus was still desperate to save his sister, so he bargained with the X-Men’s leader, Cyclops, to allow him to take a team in once a year to try and bring her back. Each year, they failed and so, by the fifth year, Cyclops forbade any more X-Men from sacrificing their lives. Colossus took a team in anyway but things went wrong pretty quickly. He discovered Magik had been completely corrupted by the demonic influence and, when she transformed Nightcrawler into a dragon-like demon, she made her bid for freedom. Colossus was forced to team up with the Goblin Queen to stop Magik from destroying the untouched area of New York. Sadly, he was too late and his sister’s demon army slaughtered the X-Men and overran the city. Using his sister’s soul-sword, Colossus fought Magik and finally killed her, putting an end to her reign. With the city lost to demons, Colossus used the soul sword to escape into another Battleworld realm with his girlfriend Domino.
In the Years of Future Past, another Battleworld domain was shown that depicted a possible alternative to the X-Men’s classic Days of Future Past story. In it, Colossus and Kitty were now married and had raised a daughter, Christina, together. They had a son as well but he had been given to Wolverine to raise outside of the tightly restricted city and the watch of the Sentinels. When Senator Kelly announced plans to ease the restrictions on the mutants, he immediately painted a target on his head. Colossus and the X-Men set about trying to save him but ended up as wanted fugitives as a result. They teamed up with Wolverine and Cameron, at which point Colossus found out that both his children were mutants. The attack on Senator Kelly was stopped but Colossus discovered that his fellow teammate Magneto had manipulated events in a bid to get Christina killed. Magneto had hoped Christina would sacrifice her life to save Kelly, resulting in overwhelming public sympathy because a young mutant girl would save a human’s life. Magneto was stopped but in a twist of fate Cameron, despite being a mutant himself, had decided that mutants did not deserve to live. He tried to kill his sister and Colossus was powerless to watch as Christina was forced to kill Cameron. With the city’s Sentinels looming down on them, Colossus and the few X-Men left took a last stand in the hopes that Senator Kelly’s voice would someday have an effect.
In X-Men Forever, Colossus had moved back to Russia when he got a call off the country’s president offering him a position on their superhero team. Once there, he developed feelings for his teammate Black Widow and the two began a relationship. One day, a man known as Cossack kidnapped Piotr’s sister Illyana with the intention of reverting her back into her Darkchilde form and using her for his own gains. By chance, some of the X-Men were on hand to help Colossus fight against Cossack’s forces. Whilst Cossack was defeated, his plan to turn Illyana into Darkchilde succeeded and Piotr was helpless to watch as his corrupted sister escaped.