Luffy vs Arlong was an easy match for Luffy, even if he suffered while fighting him it would've been an easy match for him after the 2 years timeskip. Now when Luffy arrived at Fishman Island he fought Hordy, who is 100x weaker than Jenbi, remember that Arlong is about the same level as Jenbi, Luffy suffered more than he did VS Arlong with Hordy. Remember this is with Haki ! What was Oda thinking when he did that ?
There is so much wrong with this.
1. Arlong is no where near Jinbi in anything. Do you think Arlong could fight with Ace for 5 days straight. Hell no. There is a reason for Jinbi to have a bounty of over 400,000,000 and Arlong had a bounty of 20,000,000. HUGE difference. During their flashback, Arlong was always listening to Jinbi. If he was on Jinbi's level, he wouldn't have and would of just killed humans. In fact, when they fought, Jinbi kicked Arlong's ass in the flashback. he was no match for him.
2. Hody took so many energy steroids. Each one doubles the users strength. Hody must have taken at least 50 or so. Let's put that as a number shall we. so 1 would double their strength, 2 would quadruple it. so 2^50 would make Hody 1,125,899,906,842,624 times stronger then his base. Luffy was fighting Hody that many times stronger then his base from. Luffy was even at a huge disadvantage being underwater, which weakens his attacks, and makes Hody that much faster.
Do you honestly think Oda made a mistake after putting everything into perspective like I just showed you?