What is with this notion that Goku is unbeatable.?

Dragonball basically got me into anime, but looking around there's so much blind fanboyism regarding it. Goku is incredibly strong but he's not invincible. Power level and speed means nothing when he's up against reality warpers and whole universe destroyers. There are characters who are broken beyond belief who can make it so he simply never even existed. What can one man possibly do against all that.