A-I have seen them beaten up.
This sentence can mean:
1-I have seen them get beaten up. ie. the process of their getting beaten up
but can it also mean
2-I have seen them after they had been beaten up. ie. I have seen them in a "beaten up state".
I would read "I have seen them beaten up" as meaning "I watched as they were getting beaten up". Other meanings might become apparent with additional context.