one piece manga 784
Except that Doflamingo has been put on a pedestal as being "Pure Evil". Oda has referred to him as pure evil, the last chapter was literally named "Evil's Champion". The fact that Doflamingo has been groomed since being a child doesn't exactly help the case that he could have a point of return as all it does is show that the evil is rooted just that deep within him. You compare him to Crocodile earlier I believe; Crocodile had an isolated incident of wanting to find an ancient weapon. He was a complete dick to Vivi and all of Alabasta. The thing with Crocodile though is that if you read his cover story you can find that he wasn't that different from Luffy at a point.
He was corrupted by his defeat at Whitebeard's hands. With Doflamingo the bullet list of evil deeds is much longer. Enslaving a whole country, overthrowing a whole kingdom and putting the old royal family on a pedestal of hate for the country's citizens, bringing back the Coliseum as a tournament of blood, ordering the death of Rikku's family (Scarlet), promoting experimentation on children that would inevitably lead to their death, having it covered up as "accidents at sea", murdering his own brother, creating conflict between countries so that he can sell them weapons and killing his own father. From the get go he was rotten to the core.
one piece 783 scansThere is a point of no return on the spectrum of good to evil and Doflamingo is past it. You can think of Crocodile as Darth Vader where Doflamingo is closer to Darth Sidious if Star Wars references make sense. Luffy only knows about a couple of the things I mentioned. Not to mention how much Oda has been showing us the whole "D vs Tenryuubito" side of things and how they are complete antithesis of one another. The Tenryuubito have a sour place in Luffy's heart to begin with after what they did to Hachi and what he knows they did to Hancock. Heres a new thought I came up with after lunch break. Senior Pink and Baby 5. Both of these characters have had some touching flashbacks, showing that their not as rotten to the core as the officers. In fact to me personally, both of them never really seemed evil. I can understand why Baby 5 joined, but I'm still surprised as to why a man with such "manly" dignity joined up with Doffy.
Same goes with Lao G (I mention Lao G because he showed some compassion for Baby 5 by calling her "convenient"). It seems only the officers are rotten to the core. Oda has never shown this much backstory regarding the villains so far. I feel there must be a reason to this. It could be that Oda might have writers block and is using it as a filler to buy himself more time to come up with new ideas but imo I think there might be a significant purpose to it all. Baby 5 is getting married to an ape. Lao G...died (did he really?). Senior is down for the count but not quite dead yet. I really want Doffy to end up like these three (well, maybe not like Lao G who might be dead). I dunno if Oda is just a good artist or I'm just too sympathetic, but I feel sorry for the guy. He reminds me of Obito (sorry for going off topic here).