Top 10 Scariest Alien Moments! (Including Romulus) https://www.youtube.com/watch?v=Hr55c3POsKk
https://en.wikipedia.org/wiki/Alien_(franchise)#Films
Alien Romulus (2024) Full Movie Breakdown https://www.youtube.com/watch?v=Aor_6M9JZK0
https://www.space.com/alien-romulus-has-the-same-problem-as-prometheus-and-alien-covenant
In the first Alien movie, a ship with a HUGE humanoid (engineer) is found to have been dead for a very long time in his pilot's chair. A hole is discovered indicating that something bursted out of him. These creatures seem to have been created in a lab, so as to have a series of ALIEN incursion forces at the ready.
A rapid growth Black_Liquid could be dumped onto a planet or just about anywhere, to corrupt the natural life forms.
LARGE, altered or engineered bugs would certainly make for quite a terrifying and versatile army. Some even able to incorporate the DNA of their victims in order to mimic some of their traits.
The_Pilot_(Engineer), along with his crew were somehow infected or attacked on their transport ship by the monsters.
Of course various ALIEN+movies throughout the years depict monsters and in some cases, genetically engineered or altered creatures.
https://thedigitallabyrinth.blogspot.com/search?q=ALIEN+movies