After watching the movie last night, I was left wondering: did Sentinel really deserve to die? He was only doing what he believed needed to be done to save Cybertron, a sympathisable turncoat, an Autobot leader that lost his way. Seeing how Optimus executed him was a little shocking at first, even rather un-Optimus-like. Surely Optimus would hesitate to kill his former mentor and predecessor regardless of what he did? Of course I guess there were a couple of reasons why Sentinel could not be allowed to live: betrayal of the Autobots and danger to Earth and humanity and all, but could Optimus not have simply taken him as prisoner or exiled him away from Earth? Was cold execution too far? Sentinel may have deserved the final punishment he got for his betrayal and crimes against Earth, but does that mean Optimus should have delivered it? I don't think there's necessarily a right or wrong answer to this controversial point, but it's interesting to debate. Sentinel had said to Optimus before something along the lines of: "Always the bravest of us, but you never could make the tough choices." I imagine killing Sentinel must have been one of the toughest things Optimus had to decide to do. So I guess he proved Sentinel wrong on that in the end.