I got this trophy by playing as Cao Cao on chapter 3 - starting to divide
I rushed to fight Liu bei , Guan Yu and Zhang Fei. When I entered the castle I would switch between the four R1 attacks and spam square after each one. To keep the chain active I would sometimes have to hit single a solider.
You could probably do this with most characters on any stage within a castle. Remember and don't press triangle when it flashes on the screen, that will end your chain.
Here's a link to a video of me doing it.