I chose Commander Erwin Smith and Lance Corporal/Captain Levi from Attack on Titan (I left Levi's last name out due to spoilers).

I consider these two a power couple because in my eyes, these are two characters in the anime that can truly throw away their own humanity for the sake of humanity. What I mean by this is they will risk EVERYTHING in order to win against the titans. In the anime and manga is it is clear to me these two hold a very strong bond, one I believe is very romantic but has not been confirmed at all.

Credits:
Renders done by: (all on deviantart)
shiwoo28 (Erwin and Levi)
kurotenshisasuke (Levi)
killerjeff234 (Erwin)