Calm and Relaxed are both natures that help different kinds of Pokemon. Calm will help any Pokemon that is being trained to use its Spec. Attack stat and not Attack. Relaxed will help a Pokemon that either is very slow, or is using Curse.
The only bad natures in my opinion are the Neutral ones:
Bashful
Docile
Hardy
Quirky
Serious
Even these aren't that bad, because generally that is what you use for a Ditto
the other guy like me is my little brother, lol and i breed eevee and i trade them to trainers for powerful pokemon i evolved my 2 eevees to umbreon and espeon both at lv10
It really depends on what moveset you have on your pokemon. As for the eevee nature, it depends on what the person wants to evolve it into and the moveset.
This threads pretty useless. No nature is just good/bad by itself. And as for Eevee, get a moveset for it, or if you're going to evolve it, then say that, and put a moveset, then get it rated.