This has probably been brought up before, but let's bring it up again! Okay, so I've only watched the anime. Not the movie, didn't read the manga much past the first book, just the anime series. Which is now completed. So from what I know, Wrath, Gluttony, and Envy are still alive and being their sinful selves somewhere out there. (I am open to spoilers though, so go ahead and tell me what happens to them if you feel I need to know.)
That means Greed, Lust, Sloth, and Pride are dead. Two by Roy, two by Ed.
Now, we know Ed has to kill Greed to learn how to kill the homunculi, and he has to kill Sloth to help him finally get past the "ZOMG my brother and I created a monster and paid for it with our bodies!!111'!" thing. (If you have a different interpretation, just work with me here.) So we can place Ed to the side
If you can do your math (or if you watched the series), then that leaves Roy killing Pride
Just thought it was rather symbolic.