That's some nice art there, but I think you are mistaken about the actual explanation behind Afterdeath. It's something that seems to come up a lot, with people wanting to come up with reasons why Prime might want to basically commit suicide. I'm really not sure I buy the idea in your strip that he does so because he feels guilty about the things he has done in the past? I think that misrepresents the actual events of the comic.
Anyway, feel free to stop me if you think I'm wrong.
The whole point is that Optimus and Megatron decide to have their final battle in a simulated world, not the real world. They are robots from space - at the end of the day, the digital input of a computer world is just as viable as the organic world. Megatron is even willing to play along. Yes, he's got his cheats ready, but he still has explosives stuck to his head, and once he loses for real, he doesn't rip off the explosives or crush the human holding the trigger, he just sits there and waits to see what happens. He cheated in the game, but he's still playing by the wider rules.
Megatron cheats to try to win. Of course he does. He's Megatron, he's evil. It's expected of him, in fact. The game is a simulation of reality, to replace a costly final conflict. Megatron would cheat in that too. He and the Decepticons are everything the Autobots hate - untrustworthy, low-down cheaters. Frankly if Megatron didn't cheat, that would invalidate the entire process, as that is just what he does.
Optimus Prime is not a cheat. He is a moral paragon. He leads the Autobots by being an exemplar, of enshrining total moral responsibility and the protection of all others no matter the cost. But when it comes down to it, in the final analysis, to beat Megatron, he discovers that he is willing to kill innocent lives. Yes, the computer people aren't real, but the game is being played /as-real/. In killing them to finish off Megatron, Prime has either cheated (and so forfeits the game), or he has discovered that for him, the ends do justify the means. By either of those definitions, he has lost. And thus, he is the one who must die.
It's not about being guilty. It's about realising that he has genuinely lost, 100% due to his own actions, and he must follow through with the rules.