Tatsunoko Productions were great for creating heroes that were essentially cold-blooded killers.The 60s didn't give a fukk. They made a serial mass murderer a beloved MC and hero.
Another favorite of mine is Hurricane Polymar.
Something to keep in mind as you watch this: Hurricane Polymar is a superhero with highly enhanced strength and years of martial arts training. The guys he fights are just regular dudes in goofy costumes.