Ariane 5 had some early problems, the first failure even became a case study in critical software development. But it had only had one partial failure after the 17th launch: the payload was launched to the wrong orbit because the wrong coordinates were put in the computer. A huge QA problem but not the fault of the launcher which did exactly as told.

Now, both Ariane 5 and Atlas 5 are extremely reliable, mature rockets.

Four of those were in the first 15, the last recent one was in 2018, and was a partial failure.