What G1 characterizations have been improved upon?

[Magnus]

Remember that God Magnus (RID Ultra Magnus) was never intended to be a version of Ultra Magnus, any more than RiD Grimlock is a version of Grimlock. Hasbro just reused these names to maintain trademark. I appreciate the God Magnus character too, but I don't see him as an Ultra Magnus.

Ok, fair enough. Trev did point out that there was a method to naming God Magnus Ultra Magnus, though. That said, you're right and name reassignment is by no means new.

Then in ROTF we see Homicidium Prime. The Autobots are leading NEST in hunting down the Decepticons, similar to how Cemetry Wind were hunting down all Transformers in Age of Extinction. When they found Scavenger and Sideways in Shanghai, they never offered them the chance of surrender. They looked like they were there to hunt them. Scavenger and Sideways immediately fled, and any NEST operatives that Scavenger killed was done so, really, in self defence. At the end of the scene we see a badly wounded and utterly helpless Scavenger. Optimus Prime then acts as judge, jury and executioner and executes Scavenger. They never attempted to capture and imprison these Decepticons - and we know from The Last Knight that the humans are capable of building and maintaining prisons for Cybertronians. Optimus Prime chose to kill Scavenger. And he even said, "Any last words?" before blasting Scavenger's head off -- this is at odds with what we saw in TF1 when Optimus Prime expressed regret over Megatron's fallen body, saying, "You left me no choice, brother."

Optimus Prime was already a veteran of the Cybertronian wars for millions of years, but he wasn't jaded. I find it incredulous to believe that after only 2 years he had a total personality flip just from hunting down Decepticon refugees. Really? Then there was the way that he seemed to relish killing The Fallen ("Give me your face!") -- again, totally at odds with his previous characterisation.

DOTM Optimus Prime wasn't a whole lot better, again, the way that he just executed a defeated and helpless Sentinel Prime was in the same spirit was the way he dispatched Scavenger. Another execution of a P.O.W. Even if he felt that Sentinel deserved capital punishment, surely a sense of justice would dictate that Sentinel Prime be made to stand trial first. An international court could help decide Sentinel's fate and also help the humans to understand who was responsible rather than, ya know, allow Cemetery Wind to rise up and have all the Autobots be hunted down. Cos that sucks.

Like I posted earlier, I suspect that the writers/producers/Michael Bay took note of fans' displeasure that Optimus was easily beaten by Megatron in the first movie and made him more aggressive in the sequels to compensate. Then again, even in the first movie Optimus isn't afraid to fight dirty; he kills Bonecrusher by stabbing him in the neck and decapitating him, and in the novelisation he slams Barricade against a pillar. Perhaps "any last words?" is part of making him more, well, badass.

Realistically, what are NEST and the Autobots meant to do with any Decepticons who survive to be taken prisoner? There was no place they could place or even transport them that would be capable of holding them. The idea of imprisoning Decepticons isn't even a thing until The Last Knight, and by then there are dedicated facilities for their incarceration due to anti-Transformer operations being in place for more than two years (if I remember correctly, it was six years between DotM and AoE).

Yes, "give me your face" was pretty out there, but I suppose Optimus is angry and aggressive because the Fallen represented evil in his eyes; he killed his fellow Primes and wanted to turn on the Harvester at the expense of billions of human lives. Or, again, it could be just another case of making Optimus more badass.

People like to point out that Optimus killed Sentinel without mercy, but they seem to forget that Optimus himself begged for his life after losing his arm, and Sentinel just kicked him and got ready to deliver a killing blow. Also, the context, again, is that Optimus saw his mentor side with the enemy he's spent thousands of years fighting, blackmail him and his Autobots into leaving Earth only to be attacked, and then occupy a city and attack its inhabitants. All this without Optimus even knowing that the plan was to turn Earth's human population into a race of slave labourers. I think he was justifiably angry. Even so, he wasn't proud of killing Sentinel or gloating; he gets back up and throws Megatron's gun away rather than raising his arm triumphantly or cheering.

And Revenge of the Fallen is a difficult film to defend considering that even Michael Bay has admitted it was rubbish.

At the risk of throwing this thread off-topic, people like to throw out the part where Bay seems to admit RotF was 'crap' without the all-important context. He acknowledges that the movie wasn't made under the best of circumstances and the end product suffered as a result, but he never actually says the movie is 'crap'. This is the full quote from Empire:

“We made some mistakes,” admits Bay. “The real fault with [Transformers 2] is that it ran into a mystical world. When I look back at it, that was crap. The writers’ strike was coming hard and fast. It was just terrible to do a movie where you’ve got to have a story in three weeks.”

He's referring to Sam's near-death experience where he sees the other six ancient Primes, not the movie as a whole.