Who is the main villain in the Crash Bandicoot series?

The main villain in the Crash Bandicoot series is Dr. Neo Cortex.

Cortex is an egomaniacal mad scientist whose recurring goal is world domination. He creates genetically enhanced animals with the Evolvo-Ray, intending to turn them into obedient soldiers. Crash Bandicoot is one of his experiments, but the Cortex Vortex fails to control Crash, who escapes and becomes Cortex's archenemy.

The rivalry drives the plot of the original Crash Bandicoot trilogy. Cortex repeatedly builds machines, recruits mutated henchmen and devises schemes to defeat Crash, while Crash and his allies stop those plans. Cortex is therefore the series-wide antagonist, even though individual games may introduce other major threats.

The wrong options are important characters but have narrower roles. Tiny Tiger is generally a powerful henchman, Uka Uka is an evil mask who sometimes directs Cortex, and Nitros Oxide is chiefly the villain of Crash Team Racing. Cortex, by contrast, is the recurring central villain across the main series.