I'm thinking about two types here: Type 1. Fighters who had previously shown good durability getting uncharacteristically flattened Type 2. Fighters either considered light punching or certainly not known for their punching power scoring an uncharacteristic KO with one or very few punches. Type 1 example: Kalambay v Nunn Type 2 example: Nunn v Kalambay
That is a great choice. Getting stopped by Nelson was one thing, but I don't think anyone was expecting a fighter like Grove to stop Fenech, let alone with a one punch concussive KO. That ticks both boxes - well played, sir!
Ottke-Mundine was pretty shocking when it happened. Ottke was the epitome of a feather fisted fighter. And with his professional rugby background, Mundine was presumed to be durable. The odds on KO win for Ottke had to be astronomical. (Although Mundine's chin would fail him again in some future fights).
Gianfranco Rosi knocking out Duane Thomas. Rosi ended up with 18 KOs in app. 70 fights. Most of his contests were boring. Couldn't believe the normally solid Kronk star Duane Thomas folded like a deck of cards against him in the 6th round.
Ward vs Dawson? I think dropping down in weight effected Dawson, I wouldn’t say he showed amazing durability, but had never been stopped. On the other hand, Ward had a bit of pop, but wasn’t considered a big puncher by any stretch of the imagination. A bit of a combination of both 1 and 2.