Sonnet 94 is about a group of powerful people. We don't know exactly who they are, or where their power comes from, but they definitely have some impressive abilities. Not only do these people have the "pow'r to hurt," but they have the ability to control themselves, so that they do not hurt others. Not only can they influence others, but they can also keep their own emotions in check. By the end of the poem, however, our perception of these people changes, and we learn that often the most admirable folks are the ones who are most easily corrupted.
The speaker is much more impressed by will power than by physical force.
Even though many of Sonnet 94's metaphors reference the Renaissance social hierarchy, this doesn't necessarily mean that the power it talks about is only social.