I accidentally started a war with another civ that I was friends with. What can I do to make that civ friendly with me again besides signing a peace treaty?
Some leader personalities will accept a lite warring without penalty while others will condemn you for wars they Declare. Thus, it depends.
Start by trading a peace deal in their favor. Next, give them another favorable trade. Beyond that, your best bet is to follow the normal diplomatic path to friendship: declare friendship with their friends and them, denounce their enemies, and make more favorable trades after the old benefits disappear