In general, the German Shepherd is considered to be stronger than the Boxer. This is because the German Shepherd has a larger frame and more muscle mass. However, the Boxer is more agile than the German Shepherd, and it may be able to outmaneuver the German Shepherd in a fight.
Ultimately, the strength of a dog depends on many factors, including its size, breed, health, and training. A well-trained German Shepherd or Boxer can be a powerful and formidable opponent.