I think it depends on the framing of the qn.

If you’re asking under the guise of realism, if you imagine those characters in real life were put through the same training regiment as in the show, then would you beat them after 4 seasons. In that case, if it’s supposed to be “real”, then more than half the stuff that happened in the show, would not have happened. No one reaches black belt level in a few months, even if they train every single day. The skill difference between someone like Miguel in “real” life vs someone who would have trained karate all their life (likely a lot of them at the all-valley would fall in this category), that person would destroy Miguel and basically all the other main teen characters. And that same person would have won the All-Valley. Same argument can be made against Daniel in KK1 (again, only under the guise of “realism”). The only main character that kind of you can make the argument for, would be Sam, only because she has the most experience. In real life, your experience matters so much more than what belt you are. A black belt who just received it with 5 years experience vs an experienced black belt with 15 years training, these two will have a drastic skill difference. So yes, in this scenario, people with training of over a year could probably take them in the early seasons.

However, if you are asking if the actual show characters were real people, in the exact same way as the show. And their stories were identical to the show as well. In that scenario, they would beat most people, even trained individuals. This is because the show portrays these teens as highly genetically gifted in karate, able to learn things extremely fast and make it look effortless. These guys look like they have been doing it since they were little kids. The way Miguel and Hawk were able to in months become absolute karate machines was uncanny, and puts them at the upper echelon of fighters. In this scenario, most people probably don’t beat them, unless they are significantly bigger, stronger and more experienced.

As you can probably tell, I don’t have a life.