The highly evolved salamanders. Maybe they come to the alpha quadrant to kill off us less evolved bipeds
Season 3 is probably where Voyager gains it's footing. That said, there are some stellar and stand-out episodes from season 1 and 2. The Thaw (season 2) remains one of my personal favourites. But when we hit the episode of season 3 called The Swarm, we get Voyager hitting it's stride. Granted, there are some dud episodes I find personally missable, like Concerning Flight in season 4 and some questionable episodes in season 7, that felt like the series slipped back into season 1 storytelling.