I'd like it to be Zemo.
Now as for Viper, what'sthe deal with her? I hear reports of her being used in The Wolverine, played by Svetlana Khodchenkova (whoever she is):
However, Wolverine is owned by Fox. Who owns Viper? If she's with Marvel, how can she be in The Wolverine? Why would she even be owned by Fox? Although she's associated with Silver Samurai, she's not primarily tied in with X-Men.