With Zhou Tian's strength, even though he didn't use much force in his palm strike, it was still too much for someone as weak as Hu Fei to resist.
Therefore, without any surprises, when Zhou Tian's palm struck down, it immediately killed Hu Fei right in front of him.
Just considering the situation then, there was nothing surprising about Zhou Tian killing Hu Fei. Given what Hu Fei had done, it would have been more surprising if Zhou Tian hadn't killed him. Whether for public or personal reasons, based on Hu Fei's actions, Zhou Tian obviously should have killed him.
However, even though what Hu Fei had done had forced Zhou Tian's hand, once Hu Fei was dead, Zhou Tian couldn't help but feel a sense of emptiness.
After all, no matter how powerful Zhou Tian was, he was still fundamentally just a person. While he had gained many things to reach this point, he had also lost just as much.