There are many debates and opinions with regard to exactly what is the root of all evil. Evil itself exists and manifests itself in many forms. The Catholics have even structured evil and its counterparts to formulate the infamous "Seven Deadly Sins" which encapsulates the sins of Lust, Greed, Envy, Gluttony, Sloth, Wrath and Pride.
Islam has several takes on sinning as well as evil and its origins. The Prophet (SAW) mentioned that most of the occupants of Hell would be women as women are deemed to be more fickle in nature. In these contemporary times, that would include all the men that act like women too :D
Evil in Islam includes Adultery, Murder, Gossiping, Pride, Shirk (Associating partners with God) amongst various other sins. But what is the Root of all evil? The bible says "For the love of money is the root of all evil: which while some coveted after, they have erred from the faith, and pierced themselves through with many sorrows" in the King James Version (1Timothy 6:10). But is the love of money really the root of all evil? It is evident that the "love" of money is closely associated with the need for power or authority. But money itself is not evil.
In my opinion (and its purely my opinion), the root of all evil lies in the common denominator amongst all of the other sins. It is the one sin that drives all other sins. It acts as a catalyst by adding fuel to flames which result in raging fires. It is the sin of Greed.
Greed is at the forefront of many of the major sins. St. Thomas Aquinas wrote that Greed was "a sin against God, just as all mortal sins, in as much as man condemns things eternal for the sake of temporal things". It is because of Greed that Adultery exists…because of a carnal animalistic need of excess. For those men or women who cheat on their spouses for no apparent reason, it is because of greed – because one man or woman is not enough to satisfy their desires. Greed also acts as the driving force behind the sins of Jealousy/Envy and Gluttony. When one is not satisfied with his lot, he becomes envious of his brother. Gluttony is the consequence of Greed in that it is an over-consumption of anything to the point of being wasteful. Greed is the lead actor in the play of Murder. Murder is almost always motivated by reasons that resulted from the need of excess. Robberies and trickery are also the direct result of Greed or wanting what one does not own nor has any right to. Greed is the mother of disloyalty, betrayal, violence, treason, bribery, manipulation, scavenging and hoarding as well as a host of other sins. Greed can very well be seen as the characteristic that motivates and drives most evil deeds…the root of all evil.