At the first opportunity, that Emperor-level BOSS had used all his abilities, and then, with his advantage in strength, it was quite easy for him to take down a replicated Beastman released by Zhou Tian. However, the actions of that Emperor-level BOSS at that time were of little significance.
After one replicated Beastman was killed, other replicated Beastmen immediately took its place. The efforts of that Emperor-level BOSS, from that perspective, seemed to be completely in vain.
While that Emperor-level BOSS was still unable to resist the attacks of those replicated Beastmen, his subordinates, the lesser monsters, were naturally even less able to withstand the assault from Zhou Tian's replicated Beastmen. Thus, though the arrangement of that Emperor-level BOSS couldn't be called a mistake, it ultimately only served to spare Zhou Tian some trouble.