According to TESWiki, Bandit Chiefs have 500 health. By my calculations, courtesy of the equations at UESPWiki, you can easily make a damage health potion that does over 100 points of damage. Much like in Fallout where you can reverse pickpocket a grenade or landmine into someone's pocket for explosive results, you can reverse pickpocket (plant) poisons onto someone to do damage or other affects, like Paralysis. The next method is part of the Pickpocket perk tree - Poisoned. Simply sneak up behind the target and slit their throat - easy as pie.
The first and most obvious method is the use of the Assassin's Blade perk.
