Another World Champion I had the honor and pleasure to know for many decades is Anatoly Karpov. We had many hard-fought games, including 2 Battle of the Gender matches where we tied 3-3 in both.
We also played countless blitz games. He loves chess. He loves to compete. I actually tried to model my playing style to Karpov as he was the World Champion when I started playing chess. I am thankful for our many conversations and him sharing his knowledge with me.