my opponent plays finishing move and exhausts his only ready char

can i use puppet master to negate and waste his finishing move?

Activated effects do not interrupt other players actions in Vs. but simply go on the chain. To better understand this you should consider that you need to have priority to play an effect and you only yield priority after you are FINISHED with your effects. There is no "in response to you trying to do that". This is one of the hardest things for new players to understand. Since your actived effect happened after his, although it does resolves first, his effect has already happened. You dont prevent it, you just put an effect "on top of" one he has already played

There are limited ways to stop an activated ability, see utility belt and fun and games among some of them.


In this case, he must exhaust as part of paying the cost of the plot twist. Then he yields priority, then you can play effects.

You attempt to use to puppet master to counter after the fact, but his effect is already paid for and on the chain.