I cast duplicant and then have its ETB trigger targeting [a very large] Karlov of the Ghost Council. Can Karl exile duplicant to save itself? Can Karl do anything to minimize the duplicants P/T?
Once Duplicant’s triggered ability is on the stack, the targeted creature is going to be exiled unless a spell or ability counters the ability or otherwise removes it from the stack. Killing/bouncing Duplicant has no effect on the trigger.
Duplicant will just be a 2/2 after it exiles Karlov since the counters on Karlov cease to exist when it changes zones because Karlov becomes a new object in exile.