She is a skilled fighter who is opportunistic. She was originally a human who was given specific enhancements that made her more of a cyborg. In addition to that she is fairly calm in tense situations bordering on unemotional tones yet still setting the mood with her inflections. Initially cool and confident, 18's sarcastic humor later becomes the most striking trait of her personality. Although she is mostly android she does show more compassion than the other androids.
In an alternate timeline where the androids rule the Earth, Android 18 revels in destruction and killing.