First time I read Jaime Hernandez’ work was a serialized version of “The Death of Speedy” in Deadline back in… 1991, maybe? But it did nothing for me at all, especially compared with the Hewlett/Bond showiness that was running the show and my aesthetic at the time. I didn’t go back to L+R for more than a decade afterwards, because I was entirely convinced that the two or three episodes I read had proven that it just wasn’t for me. I couldn’t’ve been more wrong.
More recently, not a particular work, but I had a visceral dislike of Ales Kot’s Wild Children, but Change and Zero completely turned me around on his work; these days, I think he’s one of the most interesting new writers straddling the Marvel/Image line.
(I was going to say Casanova, but I think my enthusiasm for the early issues based on my dislike for the most recent series has more to do with their particular content than me necessarily changing my mind.)