This is very old, but should still work if you install it manually.
Before I went at rehacking my workaround for forum badges ( by misappropriating groups ) or tried building a new plugin, I looked at @pyschobunny's nodebb-plugin-badges - but to be blunt - I can't tell what it intended to do. No screen shots or the like and installing it seems to do, well, nothing.
Anyone have any ideas?
Never finished it. (Did I publish it on npm? Oops?)
Since then there has been a few gamification plugins built, for example by @nicolas