ENTPs can be rather outgoing. They can be some of the most outspoken types... but of course not always.

If you're talking about social... then ISFP may be the most likely to be social of all the Introverts. But they can also be of few words even if they are outgoing. And I don't like to make generalizations like that anyway because sociablity is a different quality from type. It's also possible ISTP is the most energetic of the Introverted types (compared to say, INTJ)... but again, that's not always true.