This little silly here had the torso done twice because I could not find what was wrong with it. And guess what? the second one had the same problem 
(I have zero idea what I’m doing by the way) Either there’s a better way to do whatever I’m trying to do or I’ll have to restart the torso again
Thanks in advance!!! :3
Why not use the mirror modifier? Delete everything left of the center line, and then use the mirror modifier instead.
Or…
tab into Edit mode; select all; Mesh → Symmetrize : +X to -X
(When the “middle line” is not symmetric then better to not select it.)
What you can do is select the vertices of the arm that is not broken,
then you duplicate it to the Y axis.
Now select the other side with the vertices you just duplicated, press ctrl+e and click on Bridge Edge Loops.
This should work.
