If you are looking for a satisfying revenge story, don't watch this! Watch "The Glory" instead - it is also not perfect, but a more satisfying watch. Here, in Itaewon Class, the ML is driven from the very beginning to get revenge, but he has no plan. He is successful in the end but only because he is lucky and somehow stumbles into it.
It feels like the narrative they wanted to push is: you just have to be a nice guy, then success will come to you. Also, it is very slow moving, the actual revenge only happens in the last episode. And even then we don't get a big finale with a bang.

The romance that is woven into the story gets a bit too much at times and is also a bit weird, especially the unconditional love the ML shows to the b*tch character for the longest time. Speaking of characters, the character development is quite weak in general, but two characters stand out to really behave erratically:
- The young heir: obviously a nice guy, he turns evil with the snip of a finger and hates himself for it all the while. And that while being the second character after the ML who should have the highest interest of getting revenge on the old scrooge, given his awful childhood.
- The second FL, the childhood "friend". She is an awful person from the very beginning and has no growth till episode 16. And all the while she seems to hate herself, judging by the single sad face expression she displays throughout the series. I'm surprised how many reviewers rooted for her.

The series was praised a lot for its diversity: a trans girl and a black guy. Well, the creators were probably meaning well, but it ended up being quite transphobic and racist. Both characters lack depth and they get no time to explore their stories. We have 16 slow-moving episodes and the black guy speaks what, maybe a total of 10 minutes? And while I don't think that only actors from the matching minority should play minority roles, I woudn't be surprised if they didn't find a trans actress who was willing to take on this simplistic role.

Some smaller observations:
- The story spans over maybe 15 years, starting in high school. But the appearance of the ML doesn't change at all - not even his hairstyle changes :)
- Of course, severely hurt people run from the bad guys following a street, instead of hiding in bushes. And of course the bad guys chasing them by car take forever to catch up. Enough time to stop for a little romantic scene. And of course, when you have the choice of running away by car or by foot, you choose the latter. I was screaming at this stupidity.
- What are the odds of running into your unknown grandma by coincidence in a country of 50 million?