The phrase "undoubted success" means achieving something without any doubt or uncertainty. It describes a situation where the outcome or result is guaranteed to be successful. Full definition
During Arsenal's undoubted success in the early - to - mid 2000s, Wenger also relied on a solid and dynamic core in the middle of the park. (justarsenal.com)
For all his undoubted success he feels we do not rate him highly enough, and he has to belittle his competitors, to make himself feel good. (justarsenal.com)
For instance Miroslav Klose is on this list purely down to his undoubted success at the World Cup but in club football he had a very average time of it, scoring just six goals in 38 matches in all competitions. (caughtoffside.com)