Two come to mind: Flip Benham, who converted Norma McCorvey.
When Flip converted Norma (the Roe of Roe v. Wade), she was working in an abortion clinic.
The other is Bishop Thomas Tschoepe, who started the 3rd Saturday Diocesan Rosary at abortion clinics in Dallas (and the Diocese of Dallas).
The Bishop's rosary was so successful that there were numerous death threats to the bishop's office and eventually, it had to be stopped for that reason (by the next bishop).
There are other pro-lifers that should get credit as well, and the list would go on and on.
These two are notable: Flip Benham for flipping Norma from pro-abort to pro-life, and the late Bishop for starting something that often brought hundreds of people to abortion clinics on the 3rd Saturday to pray.
There was one occasion that there were so many people praying that a couple changed their mind just when they saw how many people were praying (this was near the White Rose in December as I recall).
Lila Rose!!