Justice League vs Teen Titans (2016)
Dir. Sam Liu
While the 'heroes vs other heroes' thing isn't a new concept for DC, it was pleasing to see the Teen Titans included in the continuity of the DCAMU movies because, while I'm not as familiar with the group in comic book form, I loved the 2003-06 animated series. And their involvement gave the writers an opportunity to address concerns that the Justice League might not be best equipped to tackle alone.
A connection to the Titans is made when Batman, tired of Damian's pissy attitude, sends the boy to Titan Towers in the hope that time spent with crusaders of his own age will help him to learn the value of teamwork. (And secretly he maybe just wanted some time away from the little turd for a while.)