My group in skulls and shackles once redeemed scourge... by breaking him so bad that he became a humble, fearful, and unwaveringly loyal butler to the captain.
Our group loves playing good-aligned people. We almost always try to redeem a villain unless they're absolutely evil or being so aggressive that we don't get the chance.
Some of our favorite redemptions were Ardathanus (Shattered Star) who is now living happily with a tribe of elves, Chief Sootscale and his followers (Kingmaker) who became neutral rather than evil and are good friends of the entire kingdom, and Skygni the winter wolf (Jade Regent) who was given so much meat and flattery and he decided we were his friends and stayed with us in the long term.
Of course, in Wrath of the Righteous we went around redeeming the heck out of everyone we could; Nurah, Mutasafen, Pyralisia, even a cambion who was a random encounter. His name is Baz. We love that guy.
We did also try to befriend Mister Plugg in Skull & Shackles, but that didn't work out too well for anybody. Oh well. At least we got the ship! :)
Strictly speaking, none.
By "strictly speaking", I mean that (1)NPCs were presented strictly as they are written in an APs, without any changes to motivation, attitude, and, well, actual presentation; (2)NPCs in question were actually morally changed for the better, instead of being told something boiling down to "We think you can be useful/you have nice t@+# - you can work for us, if you don't like the idea of dying on the spot".
Discounting those two caveats, quite a lot. In RotR alone the party I GMed had Erilium, Nualia, Xanesha and a significant part of Mokmurian's army switching sides, and most of them even ended up appreciably better people thanks to it.
Worshipper of the Empyreal Lord of executions, so no, not many murderers live too long after meeting me.
My PC's captured a tengu in the Godsmouth Ossuary and used him as a guide. After the adventure, they allowed him to stay with the group and even sent him off to train in a class level.