The decline of both the Han Dynasty and the Roman Empire were a slow process. What of these factors was a catalyst for the decline of both these great powers?

political infighting, child emperors, puppets, economic downturn, diseases, and etc,

Explanation:

Decline of Roman empire

-Invasions by Barbarian tribes

-Economic troubles and overreliance on slave labor

-Overexpansion and military overspending

-Government corruption and political instability

Decline of the Han dynasty

-Taxation

-The Yellow Turban Revolt

-Bad rulers

- Decline of imperial power

I hope this helps!