Saren was such a fantastic villain. I originally played the Mass Effect games out of order, so I already knew what was supposed to happen with him when I played ME1, and yet I found myself trying to convince him to shake off the indoctrination anyway. It just felt so compelling to believe that he might be redeemable, or at least that I as Shepherd would want that for him. Sovereign and Harbinger were also fantastic villains in their own right.
And then the heroes, oh my god the heroes. It’s tragic that the BioWare that could write Liara, Wrex, Mordin, and Tali is dead.