I have probably seen worse acting, but I just can't remember where or when. And the plot, sub-plots, sub-sub-plots, etc., are absolutely ridiculous The Saturday morning cartoons from my youth made more sense! Oh, and the background noise that is called (*ahem*) music is terrible, and sometimes so loud you can't make out the dialogue of the actors. Although that may be intentional, come to think of it.
Some reviewers have suggested that academy scenes are more like co-ed dorms, and the actors/actresses selected for their eye appeal instead of their acting ability. I can agree with that. And many of the reviewers that give it a rating of '1' are offended by how Indians/Hindus are portrayed. But given the political situation when the first season was filmed it was more politically correct than portraying them as Middle Eastern Islamics.
The flashbacks of the academy days at Quantico was interesting. That, and only that, was the only part of the show that made any sense. It took about three episodes to get used to the flashbacks, but they did hold my interest. If that's the way the academy really operates or if it is just more Hollywood conjecture I don't know.
The action scenes can be entertaining, if you don't let the bad acting and ridiculous plots/sub plots get to you.