Kakumeiki Valvrave 2nd Season

Same scenarist, similar plot. 

Highschool kids working together "most of the time" against the adult world. The reason can't get any more precise than that :/  

Both continue where their respective previous season left off in a serious and more involved plot this time: -The story focuses on a group of young people fighting for freedom against a superpower faction vying for absolute control. -Mysteries surrounding the mecha are revealed -The series end in a similar fashion that wraps up the story -There is no happiness but tragedy The only difference is that Valvrave is the reconstruction of the tropes deconstructed in Code Geass and Gundam IBO continues the trend of 00's deconstruction of the Gundam tropes.  

both in the futre with the people in space having edvanced meacha and start a wat except in aldnoa zero the people in space are the villians and earth is the good guys 

it is similar because they both involve with Mecha and superpowers. although code Geass is much more intense with great power and manipulative means to achieve something that benefits the whole world not just where they live such as Valvrave. I mean come on wouldn't you want to be able to command someone with the power of the Geass with just a blink of an eye. 

Both are a fun series with a grup of young people piloting badass Robots, which fights the world. Both have that that "autoparody" feel into it, with Gundam 00 being a little bit more serious in few aspects :) 

Both are about a guy who lost his humanity and have to deal with some sort of Alien-Human conspiracy.  

Piloting mechas that take something from you .. Recommending Valvrave season 2 because it's the darker and somewhat more psychological one, but of course one should start with S1. 

both of these anime are surprisingly similar. let start with the themes : valvrave theme were - mecha , friendship , death and Yolo, vampires while Buddy complex themes are : mecha , friendship and death . these anime are similar because they are like any other typical mecha anime , a inexperience teenage piloting giant robots , basically the stuff they show you in Gundams