“Come to see the ’big bad Decepticon’ huh?”
“Nah, I know just what it’s like for your memory circuits to bring up bad things that claw at your spark like a wild Predacon… and then when the pains gone you wake up and see you’ve… done things… I understand… Oil?”

Ratchet understands man, he understands.
A basic backstory to this would be Galvatron had a breakdown and lashed out during it, he fled the scene upon 'waking up' and seeing scared and angry battle-ready faces glaring back at him.
Ratchet came up to follow him and assured him it was fine, after going through the 'great war' he knows and understands it wasn't Galvatrons fault, he'll do his best to try and convince the others to give Galvatron another chance until then they sat and talked over a good drink of Oil.

This was the moment Ratchet decided he was absolutely on this sad purple sacks side and would support him. He wasn't sure at first but witnessing what happened, he now knows Galvatron is genuine in his intentions.

Proud of this one.