Is a really bad arc if you read all the continuity. Ultra magnus should know better and recognice how cheap megatron got it compared to the atrocities he did.
This is an universe where the spark can be transfered to another body, I can imagine Rodimus coming with a plan to do it with Megatron to save him and the later refusing to be saved.
I am definitely going for a third time to find easter eggs and references. The score was also great too, using motifs from previous Transformers scores including the theme of Transformers Prime, another was *Spoiler Warning* When Orion fell down to Primus after D-16 shot him, it is very similar to the score when Optimus dies in the 1986 movie. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-v1iaA9bwTe8.html The Fall - Transformers One. At 0:40 is when the motif starts, and at 1:45 you can also hear the motif from the Transformers Prime theme. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-fkjWUVu0zzc.html Death of Optimus Prime - The Transformers: The Movie. 2:10 is what to look for to compare with The Fall