If Chop Top was a soldier, why wasn't he able to take Stretch down?
I mean it's a discharged soldier who served on the front lines against an average woman, and the former has a knife with him. In reality, who would win in a fight? Sure Chop Top is completely nuts and is skinny as fuck, but still.
One, as you admitted, Chop Top is completely crazy, which makes his thought processes unpredictable and is much a detriment as anything. Two, Chop Top was given a strong electric shock recently — that messes with anybody's limbs and nerves at the best of times, but given he was shocked by contact to his skullplate (meaning that Stretch basically electrocuted his BRAIN), that's really going to mess him up. Three, he's actually not packing a knife, but a straight razor - that can cut a person, and deliver painful wounds, but it can't kill unless he manages to really press in and open the throat or a major artery — indeed, when he catches up to Stretch in Grandma's Shrine, he slices his own throat with it to show her what he's going to do to her. Finally, he doesn't lose until Stretch manages to get Grandma's Chainsaw working — live chainsaw beats straight razor, hand's down; it's got longer reach, more weight, and inflicts nastier wounds.