Shingeki no Kyojin Season 2

Both shows are sequels to two of Wit Studio's biggest works. Each show picks up right where the previous season ended. Humanity is on the brink of extinction in each show. Titans have almost devoured all of humanity in Attack on Titan. While in Seraph of the End vampires have almost wiped out humanity. Each show has giant monsters that humanity has to take out, although they are not the main threat in Seraph of the End. The main character in both shows has a mentality of wiping out all of the enemies because they killed his family. The main character can also transform into something else. In Attack on Titan Eren can transform into a titan. While in Seraph of the End, Yuu can transform into a demon. read more 

both anime feature humanity struggling against now human entities for survival  

- Great pacing as soon as one problem is resolved another even greater one appears keeping you entertained and interested. The issues are also given in a way that doesn't feel rushed or out of place. - Both shows revolve around characters in near-death experiences - Suspicions arise in places the main characters and persons around them usually call home - Great animation and sound  

Both main characters suffer at a young age which leads to them walking upon a path of vengeance. Both series have a similar production value & bring out emotions in the very same way. 

While these series are two of the best I've seen in my life, they both are kinda boring in the half and the series can be resumed in a couple of episodes. 

Both are made by the same studio and share very similar traits. -The survives of humanity are trapped inside a wall by an over powering force.  

Here you have Attack on Titan but with lolies... They are all trapped behind walls by big bad bugs. 

Both shows are sequels to shows about giant man eating creatures who have almost devoured all of humanity. More hybrids of people who are part enemy and part human are introduced.  

Attack on titan with TRAINS