Supergirl, “Nevertheless, She Persisted:” Through alien invasion, a temporarily mind-controlled super-cousin, an anti-alien weapons, the departure of her gratuitous super-boyfriend, and a teaser for next year’s big bad.
The Flash, “Finish Line:” Much drama ensues, Iris steps up, and Barry uses a technique against Savitar that he literally could have tried several episodes ago. Then we get a depressing teaser for next season, because CW still thinks we want a dark, mopey Flash.
Arrow, “Lian Yu:” Barry comes full circle, and past characters return.
Arrow: Past characters return, and then depart!! Merlyn blows off to Bermuda, and then everyone else dies on the island! it seems that the first one probably is going to stick, too.
It seems like Flash and Supergirl both basically ended the same way, but with the roles reversed, and made the whole Music Meister episode kind of moot.