Colossus and Rogue are not just two of the strongest X-Men - they're two of the strongest people in the entire Marvel Universe. Any fight that involves the two of them is going to end with a headache for the bad guys, and probably a lot worse.
But which of them is the stronger hero? Can Rogue outpunch the Russian mutant? Can Colossus overcome one of the most dangerous mutants alive? Here are five reasons why Rogue is the most physically strong X-Man, and five reasons why it's Colossus.
10 Colossus: One Punch Man
As a matter of course, Colossus is physically stronger than Rogue. Colossus' mutant ability allows him to transform his skin from flesh to steel. This provides him with enormous durability, not to mention incredible strength.
With a single punch, he can demolish solid concrete, punch through steel, and lift hundreds if not thousands of tons. There are people much stronger than him in the Marvel Universe, but in a contest of pure innate strength against Rogue, Colossus is the clear cut winner.
9 Rogue: Absorbing Power
Rogue's personal strength is that of an above-average human being. She would prove a problem in a normal fight but be unable to hang in any fight against Colossus. But her mutant gift allows her to absorb the powers - and the strength - of other people.
With a simple touch, Rogue temporarily acquires the strength of someone like say Colossus. Any fight between the two probably ends if she gets her hands on him, or if she busts out any of the super-strong people she's touched before.
8 Colossus: Carries A Submarine
A fantastic example of Colossus' tremendous strength is the time he lifted a K-14 Russian submarine from the bottom of the ocean and walked out of the water with it. The sheer strength Pitor Rasputiin displayed in this moment is staggering. A K-12 displaces at a minimum of about 25,000 tons.
Not only that, but Colossus is also doing this in hundreds and perhaps thousands of pounds of water pressure. The forces on his body are unimaginable, and yet it was a walk in the park for him.
7 Rogue: Hulked Up
Rogue has fought and absorbed the powers of She-Hulk numerous times over the years, including in X-Men: Legacy #267. She's demonstrated an ability to successfully acquire She-Hulk's powers and go big and green, with all the power of Jennifer Walters.
With the power of a Hulk, Rogue gains a significant advantage over just about everybody on the X-Men. Colossus has fought Hulk before - specifically the World War Hulk version - and it didn't go that great for the Russian mutant. Hulk broke both of Pitor's arms.
6 Colossus: Fastball Special
Wolverine weighs about 300 pounds or so, so he's not exactly a K-14 Russian submarine, but he represents one of Colossus' most powerful feats of strength. The Fastball Special is also probably the best tag-team combo move in all of comic books.
By throwing Wolverine - an adamantium missile - with all his might, Colossus extends his range and by virtue of physics, generates a serious problem for his intended target. Either Wolverine hits them on the ascent, which is bad, or the descent, in which case he could be moving at terminal velocity. Terminal for the bad guys.
5 Rogue: Stackable
Rogue can absorb the strength and mutant powers of others. She can also stack them. In some cases, including her most dramatic displays of power, Rogue has utilized all the powers she's acquired at once, making her virtually unstoppable.
Imagine a stacked-up Rogue against Thanos at the end of Avengers: Infinity War. It's probably a different outcome. With the combined strength of all the X-Men, or even the Avengers as she's also done, Rogue is off the charts strong.
4 Colossus: Cracks Juggernaut's Helmet
One of Colossus' arch enemies in the comics is the Juggernaut. Cain Marko is just about indestructible, the proverbial immovable object who has terrorized the X-Men countless times. In one head to head battle between the two strongmen, Colossus delivered a devastating blow.
He cracked the otherwise impregnable helmet of the Juggernaut. Powered by the Gem of Cyttorak, Juggernaut should be untouchable, but Colossus proves his mettle again.
3 Rogue: Absorbed Captain Marvel
One of Rogue's most startling physical feats is also one of her most tragic. In a faceoff with Carol Danvers, then Ms. Marvel, Rogue holds on to Carol too long and absorbs all of her powers, her strength, and her memories. Rogue becomes titanically powerful as a result.
With the cosmically sourced powers Carol possessed from the Kree blood transfusion Mar-Vell gave her, Rogue became essentially invulnerable. Her strength jumped off the chart, and she was far and away the most physically powerful X-Men.
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Colossus: Agent of Cyttorak 
Once Colossus cracked the indestructible veneer of the Juggernaut, really the only place he could go after that was to become Juggy himself. After Cain Marko is displaced from possessing the Gem of Cyttorak, the source of his cosmic powers, Colossus becomes the agent of the Gem in the human realm.
His strength and power amplify exponentially, and due to Pitor's nature as an already powerful mutant, the Cyttorak-imbued Colossus is far more powerful than Juggernaut was. In fact, his power was nearly as cosmic as that of Carol Danvers and other Marvel cosmic entities.
1 Rogue: Took On A Celestial
Rogue's greatest display of strength came when she absorbed the powers of not just the X-Men, but also the Avengers. With their combined strength, endurance and power running through her veins, she held off a Celestial - one of the most powerful beings in all creation - from destroying the entire Earth.
Single-handedly holding back a god-level being is pretty much all the evidence necessary to support Rogue's case as the most physically powerful X-Man - and maybe Marvel hero - of them all.