Noun
hypocrisy - Behavior that is the opposite of how one actually is, being fake by pretending to be one thing, and acting in the opposite way.

The politician was guilty of hypocrisy because he promised reforms, but his real goal was to enrich himself and his friends.
wedge - A piece of material with a thick end that tapers to a thin edge, used to split, support, or secure things; also something that forces separation or division between people or groups.

The disagreement drove a wedge between the two longtime friends, and they really didn't enjoy spending time together anymore.