Context:
I play one of my traditionnal game on endless speed and end up being attacked by Da Vinci quite early, maybe around turn 60. It didn't look really great and I thought to use the thing to finally get the achievement »How the Mighty have fallen«, that I could never get, for never being the vassal of anybody. It worked well, I lost a town and got vassalized. Then I had to free myself and did it well, with a very quick and decisive war that got me the lost town and an extra to add to my country. Few turns later, Da Vinci wasn't very happy with it and attacked me again. He lost. Then he tried a second time to reclaim what was mine, and lost again. Those 3 wars were very short (for lack of WS on his side, a 3 stars pacifist badge on mine and better fighting) costed him probably 30 troops and I lost less than 5. Then it stabilized into a bad relationship.

On my side, I however need to make him an ally and try my best, without success. I noticed that, more than 200 turns later, he still »remembers« that I did surrender to him.

Right behaviour:

One would think, that after having his butt kicked so well 3 times after that, he would forget about his victory in the ancient era...

If it matters, it is on Humankind difficulty.
No save, sadly.