From the ‘Evil Henchmen Guide’, How to Be a Villain:
Mean English Teachers
These sadistic henchmen are perfect for when you want to inflict the greatest amount of pain possible. They are arrogant, humorless, and ridiculously strict, insulting their pupils intelligence because they couldn’t become writers themselves. They can extinguish any sense of creativity once held by an individual, as well as transform previously enjoyable literary works into nightmares of horror and confusion. Their monotonous tones are capable of driving even the sanest person to the brink of insanity, useful when you are in need of a torture master. Long after a child has grown up and become a hero, the sign of a mean English teacher continues to cause fear and discomfort.
Other henchmen possibilities
Classic thugs
Mutants Robot warriors
Ninjas (winners of the Henchmen of the Year award more than any other group)
Aliens
Demented clowns
Computer programmers
Winged monkeys
The undead