Iron Fist isn't often thought of as one of the strongest Avengers, but "the Living Weapon" has shown that if he didn't hold back he would definitely be one of the deadliest. Most of Marvel's superheroes are united by one fundamental doctrine: do not kill. While this isn't a hard rule and exceptions aren't uncommon, generally what separates a hero like Daredevil from the Punisher is a willingness to cross that line. This moral code means heroes often pull their punches, as a full-strength punch from Spider-Man would be lethal to the average purse-snatcher. What happens when these self-imposed inhibitions are lifted, however?

https://screenrant.com/iron-fist-defeat-avengers-wont-kill-luke-cage/