Well personally my favorite would probably be Jellal Fernandes. Granted Jellal did some horrible stuff while under Ultears control but afterwards he and the rest of Crime Sorcière did everything they could to make up for their "sins" mainly by eliminating dark guilds and otherwise opposing Zeref and his followers whenever they could. Jellal is also one of the most intelligent characters in Fairy Tail, not quite on the level of Zeref or Mavis but pretty smart all the same. Finally the fact that Jellal survived first being enslaved, the tower of heaven, and the war with the Alvarez Empire means that there is very little if anything that could do him in. It's possible that he might die while helping Natsu and friend against the Dragon Gods but that is purely speculation at this point.