LOVE:
Catherine De'Medici- I don't think I've had a single game where we weren't BFFs from start to finish (okay, the one time I went around conquering people as Rome she knifed me, but I was already prepping to knife her, so props for doing it first. We good, we good) Her agenda is extremely easy to satisfy, and she usually doesn't do anything to upset me either (have yet to be forward settled by France).
Victoria - Either she's a free friend, or if she's my enemy, she's so far away from my capital it doesn't even matter (and her settling style is a disaster which leaves her weak and vulnerable. They should really program Victoria to hold off on expanding till Renaissance then forcefully expand via domination, unless she is right by a continental border). I also find her extremely entertaining
Gorgo - Fun agenda and keeps the game interesting, though she's rarely fond of me. I don't start QUITE enough wars to satisfy her
Philip - Usually we don't have conflicts (unless I'm playing a religious game, but in that case he's appreciated competition), and sometimes we get along
On the
HATE end, oh boy:
Mvemba a Nzinga - Dude, I just founded a religion. Give me more than like one turn to spread it. Also, stop stealing my Great People!

It's not even difficult, just irritating
Pedro - See above. Though I actually have more difficulty with Mvemba snatching them.
Qin Shi Huang - It would be one thing if I was actually trying to compete with you for wonders and snatching them all up... but I built
one.
ONE. And you denounce me. Dude, learn to use your builders for wonders instead of flooding every tile with the Great Wall. He's more or less the equivalent of Civ V Eizabeth, whiny, annoying, and woefully incompetent. Only thing he misses is her ability of getting routinely wiped out by his AI neighbors
Arabia - Mamluck + Mega-Science + Missionary Spam + Denounces anyone not following his religion. I will 100% go out of my way to wipe him out in ancient era if I spawn next to this guy, I have never had better than horrible relations. On the plus side, he does tend to be challenging. Would just like a game where we're not arch-enemies