15 [Similar Anime] Like WorldEnd: What do you do at the end of the world? Are you busy? Will you save us?

Both consist primarily of a typical slightly-moody light-novel protagonist surrounded by a harem of loli girls geared for combat.
WorldEnd's mc has a slightly better-constructed backstory and reasons for brooding, and the mc, while still (over)powerful in his own way, isn't capable of fighting side-by-side with the loli girls like in Black Bullet. WorldEnd is also more lighthearted with less emphasis on life-and-death situations.

Ok did you like Plastic Memories ? Great for you, I surely didn't. I dropped it pretty quickly because I got pissed off at the fact that the plot was full of holes just to conveniently try to jam sadness in my heart (that didn't work obviously), and it felt horribly artificial (pardon the pun while talking about robots).
However my point is, although Sukasuka doesn't have the same setting at all, the challenges put in front of the main character are pretty much the same. Except he isn't just a walking and talking dildo here just to satisfy the female cast like a VN protagonist. No, he actually is deep.

Both have a story which is based on romance and action. Although the romance takes the front seat and the action makes the story stronger. In my opinion Angel Beats! has handeled this balance perfectly when SukaSuka/Worldend could still improve a lot. But if you enjoyed Worldend you will love Angel Beats!

Same fantasy setting and atmosphere (though Re:Zero is much darker), except that the protagonist isn't being sent from the real world.

cute and colorful but sad. tired of happy-go-lucky mahou shoujo's? try this. I know you enjoyed Madoka now this should do the trick too.

Both related a novel and development of similar characters. Passing a pleasant climate even if in a heavy environment (War, discord...)

Both are post-apocalyptic fantasies revolving around a protagonist who holds a title that entails interacting with fairies. Fairies play a important role in both stories. While one is more comical, the other is more tragic. Both protagonists take their job seriously considering few have held the position.

I couldn't really say that these anime are similar in the term of story, but if we're talking about the MC, there are a few similar toward them.
First, both of the MC are secretly really powerful.
Second, both of the MC dealt with magic.
Besides of that, both of the anime are fantasy themed anime. It even aired in the same year and the same season. Both of the anime have a dark moment either. However, SukaSuka is more a romance anime, while RokuAka is more a comedy anime.

-blue haired female lead
・female protagonist in sukasuka does some action too though
-made me cry
-protagonists both are good fighters(?)

Similar to God Eater both plots have special weapons that can only be used by a selected few to fight monsters.

Giant shape-shifting monsters have all but eliminated humanity. The only way to kill the monsters is by using a specific weapon. In Knights of Sidonia humans and one personified bear live together on the spaceship Sidonia. In SukaSuka it is a bunch of personified animals and one human live together on floating islands above Earth. There are immortal characters in both series. Both shows have political commentary in them.

Call me weird but I think these 2 are quite similar in some ways.
Both has Sci-fi settings and is talking about the hardships of Military and political life, both main characters have different motives in joining but regardless, the army was not their first choice.

These shows have a different atmosphere, but a similar fate. The main characters are fighting for their life, as assassins or as soldiers, and will face death many times during the story. These are not light hearted stories, in fact, it's the exact opposite.

Gd3oWuVenCgIf you like comedically-tragic-happy-ending (that's what I called, at least), then watch this anime too...

A timeless tale of melancholic romance and fantasy, delving into story of SukaSuka gave me the most intriguing sense of déjà vu. And now I have finally identified the familiarity embedded deeply beneath my anime-watching journey – Howl’s Moving Castle.