I'll throw two underrated: Arguello and Barrera. After the Khan Molina fight, and like I've been saying for years, Khan's biggest improvement was his jab. Used it 25% before and was close to 50% with Molina. Looked pretty good doubling his jab up. Needs to stick to it instead of bending forward with his chin out
I really like Ike Quartey's jab. He is not the most effective with it of all time but it just looks freaking awesome. A lot of snap, extension, power, and form.
Close, but the answer would be Hagler. (His jab was actually a straight right, being that he was a converted right-hander.) And if we're going "P4P," then add Tommy Hearns & Pinklon Thomas. But, you know, it's Larry Holmes.
Nah, for me personally it's Whitaker. He was more consistent with it, pumping it out 3, 4 times. Hagler's had more power but still not as impressive (imo).