IPA: /ˈplɒtiə/
KK: /ˈplɑːtiər/
More inclined to create plots or schemes, often used to describe someone who is scheming or plotting.
The villain in the story was particularly plottier than the hero, always devising new plans.
The word 'plottier' is derived from 'plot' (from Old French *plot*, meaning a small piece of ground or a plan) and the suffix '-ier' (meaning one who). Thus, 'plottier' refers to one who makes or deals with plots, whether in terms of land or schemes.
Think of someone who is involved in creating or managing 'plots' — the '-ier' indicates a person, so a 'plottier' is someone who works with plots.