It is important to note that in this list we will be examining only what we have seen in the movies and actively avoiding taking anything from the comics into consideration.
Considering that Spider-Man is the only member of the team who has not reached the age of 18, coming in at number 10 on this list is even more of an impressive feat for the MCU's youngest Avenger. There may be those who are of the opinion that Spider-Man's spot should have gone to Winter Soldier (who was a definite honorable mention on this tier list), but considering that Spider-Man managed to best both Winter Soldier and Falcon during the airport sequence in Civil War, it seems pretty clear who would come out on top in a one-on-one situation with any of the heroes not mentioned on this list. While Barnes may have more mission and fighting experience, the young Peter Parker displayed skill well beyond his years in Homecoming and Infinity War, besting Vulture and, with the help of his team, nearly overcoming Thanos himself. While Bucky may have the killer instinct Parker lacks, we have to remember that there is still always Spider-Man's unused trump card should he ever need it: instant kill-mode.
9 Captain America
There are few characters in the MCU who have as compelling of a story arc and history as Steve Rogers. Captain America embodies everything that audiences love in an altruistic hero, and although he suffers from a fundamental need to sacrifice himself for the greater good, Steve Rogers has shown that he can almost go pound for pound with the MCU's strongest. During the events of Civil War, Rogers managed to bring down Spider-Man by dropping an airplane loading dock on him. (Maybe he knew he could catch it? Maybe not?) In numerous other situations, we can see Rogers using his wit and creativity to overcome asversaries much more powerful than himself. Unfortunately, his inability to overcome heroes like Black Panther, Iron Man or Thor prevent him from being placed any higher on the list.
While there is definitely potential for the Black Panther to rank higher on future lists after we have seen him develop his ability to fight with Wakanda technology, as of right now, he sits very close to Captain America in terms of strength levels and the root of their powers. While Captain America received a synthetic Super-Solider Serum, Black Panther's prefers the organic alternative heart-shaped herb found only in Wakanda's soil. After giving Captain America, Winter Soldier and Falcon a run for their money in Civil War, Black Panther demonstrated even more of his hand-to-hand combat prowess in his own feature film against rivaling tribes and Killmonger.
In the Guardian of the Galaxy films, we have seemed Gamora pull off some impressive feats of strength and skill as a fighter. She was, after all, trained and taught by Thanos himself. In addition to her superhuman strength, she is an inherently talented fighter and often the only voice of reason amongst the Guardians. Having to constantly reign in her more eccentric and peculiar team members during their endeavors says something about her strength of character as well. Gamora also marks the point on this list where human or peak-human levels of strength are surpassed. Gamora inherently has more raw power than Captain America or Black Panther ever will.
The only thing that puts Hulk above Gamora on this list is the fact that Hulk's power comes primarily from emotion. The angrier or more desperate that Hulk becomes, the more raw physical strength he acquires, giving him the edge over Gamora, whose power does have a limit. There are few who can match Hulk blow for blow in a fight, as we have seen him slam gods and rip apart battalions of Chitauri armies.
5 Iron Man
While characters like Black Panther, Captain America and the Winter Soldier often find themselves fighting to a standstill, the conclusion of Civil War-sort of-gave fans the answer to one of the most asked questions: who would win in a fight, Iron Man or Captain America? In the final fight, Stark was able to hold his own against Captain America and Winter Soldier fairly successfully. The Iron Man suit's ability to analyze the fight patterns of Captain America gave Stark the edge in that fight and, had Rogers been fighting Iron Man without the help of Winter Soldier, then it is likely Captain America would have lost the second that Stark was able to adapt. The Iron Man suit gives Tony the brawn to go pound for pound with Captain America and Black Panther in terms of strength while Stark technology and natural genius give him the edge in this comparison. In the future, when Black Panther begins to make better use of the superior Wakanda technology being developed by Nakia, the comparison between T'Challa and Stark may change. In the Hulkbuster armor, Tony was able to beat Hulk pound for pound. While the Hulkbuster armor is not Tony's typical adornment, we have to consider the fact that, should Stark ever feel the need to fight Hulk, he would come prepared with the right armor and at the point of Infinity War, Stark has made significant improvements to his armor.
At this point on the list, superhuman powers that go beyond physicality begin to emerge. Vision's power comes directly from one of the Mind Stone, one of the powerful Infinity Stones that Thanos assembles to snap half of the world away. The power of an infinity stone far exceeds anything that any of the previous heroes on the list are able to wield. For this reason, only those who have similar mystical powers are able to stand against Vision, since his ability to materialize and dematerialize at will becomes a problem for heroes like Spider-Man, Captain America, Hulk, and Iron Man, who all rely on physical strength.
3 Scarlett Witch
Scarlett Witch has demonstrated a potential that surpasses that of any other Avenger, old or new, on the roster. This potential is recognized by Hawkeye in Civil War when Clint comes to break Scarlett Witch out of the Avengers base. Vision easily overpowers Clint in a fight and becomes subdued by Vision. Vision tells Clint that he cannot overpower him.
"I know I can't. But she can," Clint responds.
Directly afterward, Wanda Maximoff sends Vision crumbling down the floors of the Avengers stronghold. During the airport scene, she also has no problem tossing aside the likes of Black Panther, one of the most physically powerful characters in the MCU. Her mystic abilities derive from the same stone as Vision, which places her leagues above most other characters in the MCU. While she is not first on this list, her placement has the potential to change drastically in the future as her powers mature.
As it stands right now, there are few that can beat Thor in a fight, especially after his Stormbreaker upgrade in Infinity War. We have seen him fight Hulk without his new weapon and single-handedly change the tide of a battle on multiple occasions using his thunder powers. While this god may have a weakness for dealing with his brother Loki, it does not seem as though even someone like Scarlett Witch or Vision would be able to overwhelm him. In the first Avengers film, Captain America and Iron Man together were not able to easily subdue him, and that was a few movies before the growth he has made to this point.
1 Dr. Strange
More powerful than the God of Thunder or the Scarlett Witch is the Sorcerer Supreme, Dr. Stephen Strange, who wields interdimensional magic and the knowledge of how to utilize the power of the Time Stone. He used this power to defeat Dormammu, traditionally one of the largest threats to the Marvel universe. While his powers were originally very fundamental, he has shown considerable growth since his original film, outmatching and outwitting the disciples of Thanos himself. These powers grant him an absolute advantage over every other hero in the MCU. The heavy hitters like Hulk or Iron Man would be easily overwhelmed by Stange's power, while the mystical powers demonstrated by Scarlett Witch or Thor would likely fall short to everything that Strange is able to wield. If Doctor Strange is anywhere near the power level of the previous Sorcerer Supreme, the Ancient One, then anyone who stands before Strange would likely fall short. The only person we have seen capable of defeating Strange was Thanos, and that was with the help of the other Infinity Stones that he was able to collect. While Thanos definitely won the battle against Strange and the other heroes (thanks Starlord), Strange did say that there was only one way to win out of millions of possible outcomes. It is likely that, despite the battle being lost, Strange will be able to beat Thanos in the war by putting together his long-term strategy. If that is the case, then the win against Thanos will be largely in thanks to Dr. Strange.
Awesome neon art by: @aniketjatav