Full disclosure: Star Trek: Voyager is this writer's favourite series. If you ask me to settle the Kirk/Picard debate, my answer is Captain Janeway, and I think Ellie Littlechild might just agree. This list is very much a bit of fun, therefore. Sure, Voyager didn't have the best track record making friends with new species, but then it didn't have the second contact teams as back-up either. Alone in uncharted territory, Janeway and crew had to make do with limited resources.
Equally, if the Alpha through Gamma Quadrants have their share of hostiles — Starfleet and the Federation have been at war with someone for most of their history — then the Delta is no slouch by comparison. There were times when Voyager was under almost constant attack, whether that was from the Kazon looking to pick up a piece of technology or the odd Borg cube/armada.
Captain Janeway might have humbly brushed off Admiral Hendricks' compliment about making "first contact with more species than any captain since James Kirk," but the truth is Voyager achieved a lot on its journey home. There were bound to be some disasters along the way, and not all of them were Voyager's fault.
Right, enough stipulations! Let's meet some aliens!
10. Deuterium, Hydrogen Sulphate, And Dichromates
That's not your next replicator order, it's the chemical make-up of the 'Silver Blood' compound with 'biomimetic' properties that Voyager — or rather Harry Kim and Tom Paris — first discovered on a 'Demon class' (Y) planet in the Delta Quadrant. Aside from some different choices in breathable atmosphere, the Harry and Tom duplicates it created were indistinguishable from the real thing.
On the silver heels of Voyager's most unlikely yet endearing besties, the rest of the crew was copied using only samples of their DNA. The fact that humans (and other species) possess a genetic memory was brought up more pointedly in the Star Trek: Enterprise episode Similitude. Captain Janeway was stuck between a rock and a slowly sinking place when she made the DNA offer, but her decision would have catastrophic consequences down the line.
The 'mimetic aliens' concept had been on the writers' room table for years. According to Joe Menosky in Cinefantastique magazine, vol. 31, no. 11, one such idea would have seen a duplicate Voyager return home, only for the copy of Captain Janeway to snap partner Mark's neck, cue theme tune. They settled on Demon, and it was Bryan Fuller who came up with the tragic conclusion for Course: Oblivion.