@Kaido:
Your comparison of Magellan is off the mark though. You said he did not relent on Luffy, but that Katakuri did. But Magellan took time between attacks, enough to allow Luffy to try getting some hits in and say words and stuff. Magellan won a lot quicker because he has poison and Katakuri has his fists and trident. You should be able to tell which of them is more deadly.
Also, is Luffy's endurance really that much of a worrying factor for Katakuri and Flampe? Katakuri being suspicious of a limit break powerup may be a bit genre savvy, but that perspective really isn't common. Let's say a TV show you watch slows down the pace a ridiculous amount, to the point where a climax really should have happened by now but hasn't. Would your reaction be to build up excitement for the climax, since there must obviously be a reason why the buildup has been this long and thus it's going to lead into something huge, or would you instead get really exasperated and plead for the end of the arc to come as soon as possible? You gave the example of shooting a zombie, but would you change your tactics if it looked like the shots were doing well enough at destroying the zombie's body? Katakuri initially had no reason to suspect a limit break sort of thing. Luffy's thrown almost everything in his arsenal at him and has barely left a scratch, and Katakuri's COO has been a security blanket to him for almost the whole fight. With a situation like that, that's not a telltale sign of any kind of buildup, that's just Luffy prolonging his eventual death. Katakuri only realized what Luffy was attempting to do like a minute ago, and sped up his attack to compensate for it. Flampe has even less reason to realize what Luffy's doing, since she doesn't know about Haki, and she's only trying to attack Luffy to gain Katakuri's favor. This fight is a credit to Luffy's strength, not Katakuri's weakness - capability is about so much more than how hard you can punch, it affects basically every fighting instinct, including resolve and learning how to improve in the fight.
Katakuri has been focused on Luffy and only Luffy since immediately after the wedding ended. In Chapter 873, he said he would take Luffy's head himself as he fears that Luffy will become a great threat to Big Mom if he escapes. He sat by and watched when Perospero and the soldiers attacked Brook and Chopper, and when he got into the action, the only thing he did to anyone other than Luffy was quickly subdue Carrot when she attempted to attack him. In the Mirro-World, he repeatedly punished Luffy for trying to stop Brulee and her goons, reminding him that the fight was just between the two of them. Katakuri would not initially have much reason to respect Luffy as he trashed Luffy thanks to his Haki and Devil Fruit and when Luffy escaped Katakuri was even fine with him leaving at that point since the difference between their abilities had proven to be enormous. But then Luffy comes back and Katakuri realizes that he's managing to close the gap. Suddenly, Flampe strikes and widens the gap again. Katakuri removes the artificial gap after discovering Flampe's intrusion on his personal goal and regains his respect for Luffy after he had been duped into losing it. People tend to view a lot of things more strongly if they find it again after losing it, and I'd easily imagine Katakuri had the same reaction here.
Katakuri's quest was never a pragmatic attempt to eliminate one of Big Mom's enemies as quickly as possible. Otherwise he could have just collapsed the whole realm in on Luffy with no way of escape. He saw it as a personal challenge to him, one that was heavily based on pride. When he jumped out to a big advantage on Luffy, it seemed like everything would stick to the status quo. He would maintain his image as the perfect undefeated warrior of the Big Mom Pirates. But when Luffy got better and it took Flampe's interference to maintain his advantage, Katakuri got mad at Flampe and dropped his act because it had failed him and prevented him from fully rising up to Luffy's new threat level.
Was Katakuri's development perfectly written? No - I think the manga could have benefitted from more moments of Katakuri exemplifying his pride to others while fighting Luffy. Maybe a direct action or display of strength from Luffy could have been sufficient at establishing himself as Kata's equal as opposed to Flampe messing around with Kata's expectations. But to me this has not been as random and forced as some people seem to think it is, and I hope it pays dividends for Katakuri beyond this arc.
So let me see if I get it:
Magellan is deadlier than Katakuri. And Katakuri is mentally slow, has tunnel vision; and in reality he didn't had honor, duty or care for his mother, family and crew; In reality he only really cared about the manly 1 vs 1 fight with Luffy. In other words egotistical. Oh, that makes everything so much better, oops, it doesn't it makes it even worse.
The problem never was that things were forced and not well explained. Have you been reading what I've been writing?
The problem is really what has been shown, that is horrible. You explaining how the horrible thing happened doesn't make it less so. What you must explain, if you want, is how what was presented is not bad.
–- Update From New Post Merge ---
@Sirxxx:
http://i68.tinypic.com/2h81gn7.png
You're welcome! Just like .access timeco. is good to know that you don't have confidence in your stance… SAD.