which character best reveal the idea of true love?

I think that Abbé Faria loves Dentes like a son. Abe admonishes himself for inadvertently giving Dentes the taste for revenge:

I regret having helped you in your investigation and said what I did to you," he remarked.

"Why is that?" Dantès asked.

"Because I have insinuated a feeling into your heart that was not previously there: the desire for revenge.