Complex sentence: In "The Lego Batman Movie", Flash is seen attending Superman's party, and asks Batman to take a picture of the whole Justice League, leaving Batman disappointed because he wasn't in the picture, despite being a member.
Split into simpler sentences: In "The Lego Batman Movie", Flash is seen attending Superman's party and asks Batman to take a picture of the whole Justice League. This leaves Batman disappointed because he wasn't in the picture despite being a member.