indefensible - Unable to be defended, justified, accepted, or excused.
impressionable - Easily influenced by somebody or something, usually due to being inexperienced or naïve.
inevitable - Certain to happen and impossible to avoid.
infiltrate - To secretly enter a place, organization, or group, often for spying or sabotage.
incendiary - Likely to cause fire, violence, strong feelings, or anger.
impressive - Eliciting admiration or respect due to excellence, skill, or ability.
impervious - Not allowing something to pass through; impenetrable; not affected or influenced by something.
ineffable - Too great, powerful, or beautiful to be described in words.
induce - To persuade or influence someone to do something.
inertia - Resistance to change, effort, or progress in a situation, system, or organization.
incline - A slope or slant, especially a surface that is changed from a horizontal position
inclination - A tendency or preference toward something; a liking or desire.