I guess mine would be a tie between Virion & Cherche and Virion & Fredrick.
Virion is a character I did not like before finishing a fair share of his support logs. He was gross is his interactions with other characters and most of his C rank supports boiled down to characters bing put off by his sarcasm and unwanted flirting. Eventually though, the Shepards come to realize the he is good person with a bit of a tragic past. By the time I finished his A rank supports Virion had gone from being one of my least liked characters to one of my favorites.
Best quote though goes to Avatar(F) & Gangrel. For their S rank support he wants to celebrate by, "slaughtering all the livestock they can find!"