The single greatest feat of strength seen by Steve Rogers in the MCU movies was in Age of Ultron. In the siege of the Hydra base, Cap is seen flipping his motorcycle (a 2012 Harley-Davidson Softail Slim or a Harley-Davidson Street 750) over his head, into a Military grade Humvee. Dry standing weight of these bikes are in the 600+ lbs range. That's not including any upgrades or armor added.
Not only does he flip it while at high speed, he stops the Humvee in its tracks. And he completely negates all forward momentum of himself, ignoring inertia.
The record for human weightlifting is ~400 lbs snatch, i.e. a clean lift above the head. Cap did it without any signs of exerting himself. This puts him into superhuman range, clearly not peak human. Steve's Strength, stamina, speed, and athletic/gymnastic skill would allow him to easily break every single Olympic or Guiness record by a large margin.
In Civil War, we see Cap single handedly hold a helicopter in the air.
Based on a comment by TylerH on similar question:
The helicopter in the movie generates about 2000hp, or 1491.4 Kilowatts. As shown in quora.com/How-much-energy-can-a-human-produce and en.wikipedia.org/wiki/Human_power, as well as worldbuilding.stackexchange.com/questions/32336/…, a healthy human (on average) 1.2 horsepower for a short time, whereas a trained athlete can generate twice that. Considering Cap is capable of holding that helicopter indefinitely, and thus generating at least 2000 horsepower... He is being shown as able to generate ~1666x as much power as the average human. That by very definition of the word is superhuman ability.
Rogers ability to stop a helicopter for a significant amount of time is just inhuman.