User blog comment:Roranoa Drake II/Chapter 790: One Punch/@comment-24850639-20150618173236/@comment-10543621-20150619034418

To be fair, when Doffy said that he would not underestimate Luffy, he DID attempt to no underestimate Luffy. He put up several measures against him, but each one of them steadily failed. The difference is that he expected that his efforts of NOT underestimating Luffy to be sufficient in stopping him before he causes all the chaos, but unfortunately, that still failed.

Obviously when faced with the crunch, it's no longer about underestimating his opponent, It was more of him reaching his limits and not coming to terms with the fact that he's actually been pushed that far. I guess, you can say that his attempt at not underestimating Luffy was still an underestimate. Meaning, he wasn't gonna think that Luffy was some small time bait with no threat like other adversaries had, but at the same time he certainly didn't think that Luffy would be strong enough to bring him down. I mean, based solely on experience, Luffy is still a major rookie. Doffy spent years amassing his influence and abilities, it's almost impossible for someone like that to NOT underestimate his opponent to a certain extent. He probably expected them to pose as a problem to him, and he did prepare for the problems he would cause, but he certainly didn't expect the problems to mount up to that level.

I do agree on the whole reverting to Gear 4 after that flashback though. I for one was expecting something completely unexpected, and definitely not another Gear 4 mega punch. Then again, I guess that itself was kinda unexpected? In a way it fits Luffy perfectly. If Kong Gun didn't work, we'll just go even bigger with a King Kong Gun. I guess one could argue that Gear 4 would be completely undermined if Luffy revealed yet another technique so soon after the hype Gear 4 received.