Season 3 Decepticons stole all the character growth budget.
G1 Galvatron showed the greatest growth here:
(cued to 2:50)
with G1 Galvatron and G1 Optimus Prime shaking hands and making peace. Their relationship fully developed.
Optimus Prime also himself grew a lot along with everyone else; he even said we’re all a little wiser now and it’s up to us to fill the Matrix once again.
It doesn’t get any better than G1 Optimus Prime leading his Autobots saying, “Autobots, transform and roll out, “ and driving off into the sunset.
No one questioned his position as leader, not even Hot Rod, Kup or Ultra Magnus. They stepped down and moved out of the way, stood to the side, unlike Bumblebee in RID 2015, while the humans apologized to him. They knew who was the boss bot, the big cheese. Heck, even G1 Galvatron stood in line behind the humans waiting to shake G1 Optimus Prime’s hand out of respect.
Sidenote: Why is G1 Optimus Prime shorter and smaller than Hot Rod, Kup, Galvatron, etc. in Season 3 when he was bigger and taller than most everyone else in the first two seasons. G1 Optimus Prime is a Semi-Truck; Hot Rod is A Lamborghini. His tech spec even says he’s the largest Autobot.