I propose 2 (imo better) alternatives to Predators and Xenomorphs.
1. The Consu from Scalzi's Old Man's War trilogy (highly recommended easy reading sci-fi books).
They reminded me of Predators in a way, but are even more badass. First, they are by far the most advanced alien species in the known universe. To give you an idea, here's a quote from the chapter where we are introduced to the Consu:
"
Striking first against Consu was not an option. Their entire inner home system was shielded. The energy to generate the shield came from the white dwarf companion of the Consu sun. It had been completely encased with some sort of harvesting mechanism, so that all the energy coming off it would fuel the shield. Realistically speaking, you just don't fuck with people who can do that."
Second, they stage ritualistic battles against other alien races (humans included). What's so cool about that, you ask? Of course, if they were serious about winning they could easily steamroll anyone in a heartbeat, but instead they downgrade their equipment to match the power of whoever they are fighting against that day. That's a lot more badass than what the Predators do, because the Consu actually allow for a fair fight.
And third, they are terrifying looking. Scalzi's descriptions are usually vague enough that depictions of the various alien races vary a lot between readers. I imagined the Consu as 8-foot tall bipedal lobster-like horrors. Here are some fanart depictions of Consu:
credit to James Stowe said:
credit to John Petersen said:
credit to Shawn Witt said:
I could go on, but anything else would probably contain spoilers.
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2. Tyranids from Warhammer 40k. I have never played a Warhammer 40k game or read any books, but I once went on a Wiki binge reading about all the crazy ass aliens in their universe. The Tyranids were so awesome that they became one of my favorite alien species in fiction. And by awesome I mean the most horrifying thing imaginable. They are basically Xenomorphs on mega steroids. Here's an excerpt from the Warhammer 40k Wiki:
"
The Tyranids are an extragalactic composite species of hideous xenos that is actually a space-faring ecosystem comprised of innumerable different bioforms which are all variations on the same genetic theme. . . The Tyranids collectively form a monstrous superorganism that travels across the universe in their great Hive Fleets of biomechanical Hive Ships, systematically consuming all other biomatter to enable its own rapid evolution and reproduction. All Tyranid organisms are synaptic (psychically-reactive), and each Tyranid creature within a Hive Fleet shares and contributes to a communal Hive Mind, which allows the trillions of beings comprising the Tyranid Hive Fleets to communicate and organise instantaneously on a staggering scale."
Here's some pictures of these horrors:
Here's a pic of their bio-weapons. Yes, they create all of their weapons and vehicles out of bio matter:
Constantly and rapidly evolving, spawning terrible creatures of all sizes (some capable of bringing down spaceships), deadly, relentless, and quick to learn and adapt to the tactics of their enemies. Awesome.
They've got a complicated honor system, they have lots of nifty gadgets, and they look cool.
I mean, I'm not usually one for dreadlocks, but they can pull it off.
I know I threw some shade at Predators above, but I still think they are awesome. Definitely one of my favorite alien races in fiction.