The prominent actor who faced significant challenges in their career despite early success is Robert Downey Jr.. After achieving stardom in the 1980s and 90s, struggles with substance abuse led to multiple arrests and career setbacks. However, Downey managed to turn his life around, leading to a remarkable resurgence with roles in blockbusters like the Marvel Cinematic Universe. His journey illustrates the importance of resilience and personal growth in overcoming adversity in Hollywood.