When JoJo and Wamuu part in friendship after the former kills the latter. They may have been enemies, but such was their admiration for each other's cunning and bravery that there was no hatred, only a warm understanding and respect as JoJo gave the ancient warrior his blood to ease the pain of his passing; and Wamuu only dispersed as dust in the wind when he was certain that JoJo took his antidote, dying without regret having met such a great warrior.
Wamuu: I don't have any regrets... I am sincerely happy to have been able to witness your progress. Maybe I roamed more than ten thousand years just to meet you. Farewell, JoJo.
In a way, Wamuu promising to hold Caesar in his memory. It shows that despite his nature, Wamuu can hold respect for people that aren't him, and can find something worth remembering in them.
For context, Wamuu put a poison ring inside Joseph as a way of ensuring the two would fight once Joseph completed a month of Hamon training, as he would have needed to defeat Wamuu and take his lip piercing (which held the antidote). Caesar fought so well that he nearly came out victorious, only for a last-second slip to give Wamuu the advantage. Using his last bit of energy, Caesar managed to rip the ring off Wamuu's lip and create a Hamon bubble from his blood, intending to send it to Joseph. Wamuu could have burst the bubble easily- and he chose not to. He had enough respect for Caesar that he considered the debt fulfilled, allowing Joseph to live in honor of Caesar's bravery and skill.
The fact that Kars, a villain, cares for his comrades. When Wamuu attacks him for stepping in his shadow, Kars merely acknowledges this as him acting on instinct and apologizes to Wamuu. Later, Joseph himself noted that he could sense the hatred that Kars had for the former because of killing Esidisi. Then when Wamuu dies, he writes off his sense of honor as a flaw that made him weak... and then kills a group of vampires that spoke ill of him.
Doubling as an awesome moment: Joseph's very first strike in his battle with Esidisi. Joseph was originally headed to the arena to spar with Loggins, but Esidisi got there first and killed him with a single kick to the lungs. To a Hamon user, this is both an insult and an extremely brutal way to die, so Joseph stealthily ties an oil-soaked thread around Loggins' finger and pulls it taut into Esidisi's wrist.
Joseph: First blood goes to me, and my instructor!!
When Joseph managed to defeat Esidisi, he thanks Loggins for the training.
Joseph: My Instructor, I must thank you for torturing me. Grazie, Loggins.