They caused the whole disaster in the pursuit of ilicit gain. They pull a gun on the heroes and foil their flawless plan for survival/killing the monster. They were secretly helping the monster all along. They steal the escape vehicle for themselves. They leave you to die. And they telegraphed all of this a mile away with their condescending remarks, complaining, cowardice, and general assholeness throughout the entire plot.
This character is present in almost all monster movies and disaster films. It refers to any character among the survivors who eventually ends up betraying the others to ensure his or her own survival or accomplish some deranged, illogical goal that benefits the monster…all of this usually occurring about 3 minutes before the character is eaten by the very monster or killed by the very disaster they betrayed the other survivors to avoid or assist, always resulting in an Ironic Death. The audience, naturally, saw this coming a mile away. The character was being a jerk all the way until now, constantly pooh-poohing every plan the protagonist made, complaining often, perhaps having been revealed to have a financial stake in whatever circumstance got the protagonists locked in their current situation (such as engineering the monster or arranging for whatever situation isolated everyone from help), hitting on the females, moaning and complaining about how he/she is too rich/important/whatever to be in the current situation, possibly emotionally breaking down to tie everyone up, etc. Occasionally, the character will also be the Load, and is a good candidate for one since the audience feels even better when the Omega Jerk dies than the Load, who can be an innocent vicitm as opposed to someone who was in need of a visit from karma.
The “omega” part refers to the fact that as much as the jerk had it coming, some circumstance at least managed to preserve them from the initial disaster that isolated everyone else from help or killed all other survivors, and that usually the jerk was part of an organization of jerks that have progressively gotten whacked, leaving him the last one but no less jerky than the others were.
The Omega Jerk is almost always illogical in their actions where they are not motivated by survival, as their betrayal will almost inevitably result in their deaths. However, they might still do this out of a desire to accomplish what they consider a “Greater Good” or further science or anything else, although these are usually mad goals in and of themselves.
The Omega Jerk usually gets his/her comeuppance in one of two ways:
1. Gets immediately killed on whatever escape route he/she took. (Which at least proves to the protagonists that they shouldn’t have used that option anyway.)
2. Dies as he/she tries to get in one last “Reason You Suck” speech to the protagonists, often from the monster sneaking up behind them.
It should also be noted the Omega Jerk doesn’t always get his/her comeuppance in the form of death, but they will always get an Ironic Punishment at any rate.
The Thing from Another World – This is the earliest example of an “Omega Jerk” I can find. Carrington clearly cares more about ensuring the thing’s survival than the survival of the rest of the team at the arctic station. Eventually his attempt to both save the creature from the team and “make friends” results with only being smacked down by the monster, although he manages to survive.
Alien – Ash is not a “true” Omega Jerk in that he doesn’t meet the comeuppance condition (his incineration was not directly a result of the alien he was trying to protect), plus he’s not the last of a surviving group of jerks, although he represents jerks on Earth. However…
Prometheus – David does.
Aliens – Burke, obviously.
Night of the Living Dead – Cooper.
Deep Rising – Canton.
Virus – Everton. Possibly Woods too.
Resident Evil (video game) – Albert Wesker.
Resident Evil 2 (video game) – Ada Wong, Chief Irons, and Annette Birkin.
Resident Evil 3: Nemesis (video game) – Sgt. Nicolai.
Resident Evil: Extinction – Dr. Isaacs.
Resident Evil: Afterlife – Bennett.
The Mummy (Brendan Fraiser version) – Beni (sort of).
Pretty much ever Sci-Fi Channel Original Movie ever made involving survival (against monsters or disasters) has one.