In some ghost stories, the ghosts clearly died so miserably, yet they don't go seek revenge on their true enemies, but hide in dark corners bullying the weak, which seems really low.
You have such skills, don't just scare little kids, go and duel with the three-eyed guy who leads the dogs?
Annihilation went in a completely different direction.
No one knows what her original form looked like; maybe she was just an ordinary member among the countless Federation mutants, but in the Federation Consortium's cruel experiments, she was forced to merge with the flesh and blood of countless mutants.
If that's all, she would just be another statistic among the victims of the Federation Consortium's inhumane secret experiments.
But due to internal policy changes in the consortium—perhaps because of a presidential election, or maybe a diversity department manager had a sudden bright idea, or Smith was anxious for progress.