Back in 5th grade I used to do shots of fresh-squeezed lemon juice when my parents weren't home, so when I tried Warheads my reaction was more "that's it?" but they were OK.
Morbid Mouth was the only sour candy I've tried that was actually very sour, but it was pretty much just a test tube full of the sour powder from the outside of a Warhead. There was some kind of candy that was just liquid sour flavor that used to come in tiny bottles in the late 90s and I remember it being fairly sour too, the time I tried it.