Honestly, i could write a list of headlines to describe this work but it's not even worth the energy.

DO NOT WATCH.
(Or do but be prepared for the disappointment)
Can you guess where it belongs? A GARBAGE BIN because it's a pile of ABSOLUTE RUBBISH.
I didnt read the webtoon but maybe it's better written there even with the same narrative? i dont know...

This 2nd season has no relation whatsoever to the first. If this was supposed to show me how the classmates have become a true one unit highly dependant on each other, cooperative, considerate, then it's done so really badly. The pace is unbelievably slow with noooo real progress in the depth of their connections. Suddenly people are a couple and there's a love triangle like what? What situations led up to this in the first place? We definitely do not get to see that. The villian at the end? No true long time build up; it just escalated like that out of the blue because the writers forgot there's got to be evil to get a closure.
The post-credits scene was unnecessary and should have been in the first season. The addition would have been great as a comedy relief and as a nostalgic tribute. After the ending of season 2, it's almost pointless to see.
I like to believe, as many others I'm sure, that the true ending of the series is either episode 6 of season 1, or the pre-credits scene.
I gave points solely to honour the idea that on our Earth there's something much more worse than human-eating aliens, and for highlighting the pressures of being a high schooler in Korea (albeit extremely dramatic really). But story wise, direction wise, acting, everything was terribly executed. There's even an episode or two that are entirely useless..

P.S. If you really want to watch it, do so at 1.5x and save yourself some time instead to use on a better written work.