This is a story I read about 15 years ago (or maybe 20?) within an anthology book of sci-fi stories that was already old when I read it. From what I can remember, the story goes like this:
An alien wakes up in a lake and using the energy stored within him (thanks to the advanced technology of his race he can store energy and use it for different purposes) walks over the lake and crosses the lake to talk to the natives (frightening them by walking over water, of course).
When talking with them (he can do it thanks to his advanced tech), he realizes that they are so primitive they don't all love each other (which is the peak result of any advanced civilization).
He sends a beacon so their partners rescue him.
Then, he tries to help the natives so they all love each other. Meanwhile, he uses the energy within him (or his suit) to heal people, to produce food and even resurrect a couple person.
All of this causes a commotion within some of the natives who then capture hil and "kill" him.
He would try to fight back if it weren't because he's low on energy, so he apparently dies but actually goes into stasis until his race returns.
A couple days go by and his race returns and takes him back, in front of many witnesses.
There could be some details of the story that are different, but I'm almost sure that the story was like this. This anthology book where I read it was in Spanish (I'm from a Spanish-speaking country), but I don't think the story was written originally in Spanish (although it could be, I don't really know).
I know it didn't involve time-travel for sure, so it isn't a story about that. And it was on planet Earth.
Does anyone know it or heard of it? I tried finding it for the last ten years but no luck.