You can craft shock combat gloves that deal extra electrical damage. Bare fist don't have the option. Both will need expose weakness against high tier robots like Naga and Industrial bot.
I would say all melee weapons have some sort of weakness. High DEX melee build can eliminate their weakness by taking Versatility feat (W2C ammo, acid chem pistol). Otherwise your options are the usual grenades, traps and caltrops.