My couple top favorite things were:
-The protagonist's growth. He starts as a wimp desperately trying to have sex with any hot women that shows up. But eventually after everybody else dies he starts taking responsibility, not only fighting the aliens head on but also providing leadership to the newbies and even figuring out the normal girl next door has feelings for him and so starting to date her. And when eventually super hot idol falls for the protagonist, he makes it clear right away he already has somebody in his heart and will stick with her.
-When said idol that got dumped just decides to exploit the setting's mechanics to get a copy of the protagonist to serve as her personal boyfriend. In particular because it explores the whole "replacement clone" aspect that shows up in plenty of media, but rarely taken in account that you don't need to wait for the original to die to make a copy. Plus hey, a pretty nice way of solving love triangles. Also hilarious when the protagonist meets his clone and one of them goes "Wow, talking to myself like this, I ralize how much of a d*** I can be".
And I would consider that exploring "the depths of human depravity" isn't necessarily a bad thing. In particular when characters often get punished by it, like that other dude at start who tries to abuse the "you can use your super weapons against anybody between missions as long as you don't leave witnesses" and ends up having his head bomb detonated. Similarly body horror may not be everybody's cup of tea, but there's plenty of fans for that. (cough Franken Fran cough).
In the other hand the vampires aborted plotline and all the bs being pulled during battles were plain bad yes.