I am not talking the Warlords, but the Territory whe know as China -- with lots of little independent Kingdoms like the HRE.
DuQuense
If you want something fairly permanent, without a strong desire to 're-unity' the empire possibly the best bet might be just after the establishment of the Han. I was reading a few months ago about this.
The Qin 1st emperor had been a very nasty type and caused a lot of death and destruction. His son had been a pretty incompetent character by most accounts and this had trigger a period of civil war as a number of userpers had rebelled against him. The founder of the Han dynasty, you seems to have been markedly less capable than one of his rivals had finally won out after another period of war.
During the Qin the emperor had also advanced the empire's borders to the north, securing the land inside the loop of the Yellow River, which had previously been occupied by various pastoralist peoples. In response they had established a confederation and during the civil war period reclaimed the territory.
Now the 1st Han emperor organised this huge army which he led north to defeat them and reclaim the land in turn. However he was totally out-manouvered and the entire army forced to surrender.
That's all OTL. Apparently the leader of the confederation was initially intending to slaughter the entire army, including the emperor. However his wife presuaded him to make peace with the Han who realised they could gain influence over the northern tribes by economic means trading with them for items they couldn't produce.
If the army and emperor had been killed it would have led to further instability and disorder and probably another period of civil war. Also at the time much of what we think of as the Chinese heartland was occupied by people who did not consider themselves Chinese and this continued for another few centuries.
Therefore possibly another round of conflict and chaos coupled with strong non-Han communities might have persuaded enough of the Chinese they were better off with smaller, local kingdoms rather than all the problems of someone seeking to establish an over-arching empire, which means crushing everybody else. Possibly some groups unite to defeat one powerful claimant then, rather than agree to one of themselves being an emperor, or falling out over the issues and triggering yet more conflict, decide on an alliance to protect themselves and prevent anyone claiming a centralised throne.
It would be difficult because I think Confusious ideas had already got quite a grip on the Chinese intellectuals but might be about the only way of permanently breaking the idea of empire without massed slaughter of the sort of scale that possibly only the Mongols under Genghis could have tried.
Steve