Menma had no special feelings toward Haku.
At most, he regarded Haku as a whetstone for himself. He had no psychological hesitation whatsoever about killing Haku. It should be said that this was the way a normal ninja ought to think. You were the enemy, you wanted to kill me, so I killed you. That was only natural.
Besides, after the buildup and trials he had gone through before this,
Menma was already able to face killing as though it were ordinary. This was the truest reflection of this world, and also the "routine" Menma had to quickly adapt to.
Sasuke was the same.
Looking at the Mist Ninja lying in a pool of blood, already devoid of any sign of life,
Sasuke's expression did not change in the slightest.
Compared to the hell he had once seen,
this was child's play.
Only Naruto still wore a somewhat unnatural expression. Even though he understood perfectly well that killing ninja from an enemy village who had come to attack them was normal, after twelve years of almost greenhouse-like instruction in Konohagakure, this was not something just anyone could adapt to quickly.
That was also why Naruto had hesitated at the very last moment.
Just as Menma and the others finished surrounding and killing Haku, on the other side, having lost Haku's cover, and with Kakashi no longer holding back as he had during their first clash in the Original Work but instead going all out,
Zabuza truly was no match for Kakashi.
Elite Jonin could differ greatly in strength as well.
Crackle, crackle, crackle, crackle, crackle!
The lightning burst forth wildly!
Boom!
A terrifying force surged forward with a roar.
With the Ninja Hounds having completely restrained Zabuza, Kakashi thrust straight ahead.
Squelch!
He easily broke through Zabuza's final defensive struggle