The race-specific events in my experience are mostly positive. For example, Ackdarians may suffer from attacks by giant sea monsters, but they can also gain fairly significant yearlong happiness bonuses at colonies with Nepthys Wine, and to my recollection the wine event is much more likely to occur than the monster attack. Another example, if I recall correctly, is that one of the other species can get a minor increase in the quality of colonies on certain types of planets (only one colony for any given event, though, not all such colonies at once).
I'm pretty sure that the giant sea monster attack is both the worst event in race-specific events (or at the very least close to it) and one of the few bad ones, and since the damage to the colony is only temporary it's not really that bad in the long run.
After playing with 'Disaster and other events', it seemed like there was no such thing as a random 'good' event, just all disasters. to be fair the first part is labeled as disasters so I expected that, but kinda was hoping the 'other events' might include some good random events. Maybe just unlucky but hadn't gotten any good ones, just bad to super bad
There are a handful of positive events tied in with disasters and other events; for starters, there's a "discovered new source of (some resource) at (some colony)" event, which adds a random new resource deposit to a random colonized planet or moon. But yes, most of what's in disasters and other events are negative events. I personally feel that some of the negative events in Disasters and Other Events are actually among the more entertaining events in the game, as long as you don't have a run of bad luck and have to deal with them in one game after another.