When it comes to the final two choices, I am going to go with this vote:
Sephiroth x GLaDOS
My reasoning for choosing to vote for Sephiroth is because he shows up in Final Fantasy VII, Crisis Core, Advent Children, Last Order, Kingdom Hearts, Kingdom Hearts II, two of the Itadeki Street games, Ehrgeiz: God Bless the Ring, Dissidia, Dissidia 012 duodecim, Thearhythm, and Thearhythm Final Fantasy Curtain Call. Plus in Dissidia and in Dissidia 012 duodecim, he is playable. Where as GLaDOS only shows up in Portal, Portal 2 and Poker Night 2. Also GLaDOS is never playable.