When Luffy enters Impel Down he eventually runs into Mr. 3 and frees him. Although Mr. 3 holds a grudge against Luffy he seems to have developed some sort of honor or code and refuses to not pay Luffy back for rescuing him. I do not know if its an altruistic thing, but rather Mr. 3 just does not wish to feel indebted to Luffy. During this time we also are revealed his real name is Galdino, but most people still refer to him as Mr.3. He once against uses his Devil Fruit abilities in very affective manners against tough opponents. Even though Luffy is battling a very tough foe Mr. 3's wax powers enable Luffy to get an upper hand. It goes to show you that the Devil Fruit power can be beneficial even if it seems weak based on how one uses it. This idea is most evident when it comes to Mr. 3, because he takes a seemingly harmless Devil Fruit and uses it to it's maximum. During the War Mr. 3 even becomes instrumental in Luffy's attempt to rescue Ace. He even goes so far as to risk his own life in the effort while previous he only showed regards for himself and was pretty much a coward. He like many of the former Baroque Work agents would come to be somewhat of an ally or friend to Luffy.
Mr. 3 began as a asshole villains who only cared for himself and was overly arrogant and mean. During the Little Garden arc he was the epitome of an evil villain cruel, ruthless and uncaring. These were very good traits for a villain even though they were a bit cliched. His physical design as well as his powers were definitely interesting and unique to him alone. Over all he made for a memorable villain even though his screen time was limited. This maybe why Oda decided to bring him back into the story and develop his character even more. The whole face turn of Mr. 3 was brilliant writing and showed how much Oda can develop and change a character over time and through different circumstances. By the time in the sotry now Mr. 3 has under gone some of the most radical and interesting character devlopment of any of the non main cast. As of now I think most people would view him as somewhat of a good guy and not a villain anymore. He to me was truly redeemed and changed from his original incarnation by the time I am writing this. So to me he is truly was on e the classic villains and very important to the story that is One Piece. So feel free to give me your impressions of Mr. 3 and what you all think about him and his transformation.