I've mentioned several fighters who have lost their pro-debuts and wen't on to do good/really good after. Some that I remember;

Lost Debut:
B-Hop - Lost debut P4P fighters of our times, argueably top 3 Middles of all-time
Arguello - Do I really need to explain what happened after? (Maybe just for Taeth )
R.Marquez - P4P fighter just like hes bro, skilled and powerful.
'El Maestro' - Argueably the best Fly of all time, one of the most skilled fighters ever.
'Homcide Hank' - P4P all time who lost his debut in KO fashion.

Lost early in career:
Cazares - 1st fight was Draw, wen't 2-3 in 1999 but hasn't lost since 200
Sanchez - No need to comment really.
Azumah - After his loss to Sanchez he went on to do some major things in boxing, BHF to name one thing.
Pedroza - Lost early but is a superb fighter, BHF.
Monzon - Lost in his ealry career, now P4P all-time and IMO #1 Middle ever.
E. Griffith - Lost early in his career and wen't on to do great things in boxing, IMO very underrated (because of lack of footage of him
available for people to see), BHF.