From the moment we first met him on Namek, it was obvious that Dende was not a fighter, but definitely someone willing to put it all on the line for the good of his people and his planet.
There were a couple of close calls on Namek where he was threatened
by Frieza and his men, but Dende made it out of there alive. He ended up on Earth, and became the guardian in the place of Kami, at Goku's personal request.
As a guardian, he assumes the role of a deity, or god, on our planet. Dende still doesn't have much actual fighting power, but he's always had something that Goku can only dream of - an amazingly useful healing power. But let's face it, in a real fight with Goku, Dende wouldn't last a millisecond.