First up for the limitations is
@nico.
This power is pretty straightforward but still, I have some more things to ask.
What exactly are the perquisites needed for being able to possess someone? Name, face, and location? You mention she has to know their face. What do you mean with a name actually? If, say person x goes by Jaiden but is actually called Holly, which name do you need to know to properly possess them?
How close to a person do you have to be? Maybe this could depend on the information you have. Say if you know face and name you can be 200m away or something like that (you decide, just not super far) but if you only know where they are (in a room and you have to pick one out of the crowd) then you have to be like 10m away something like that?
also, how far with the possessed can you wander before having to return? Does the possessed have any recollection?
And you mention using other's powers. What do you EXACTLY mean with 15%? Pick a very physical character like Trinity (superstrength type character, think Superman) If she can lift 15 tons, can you lift one? Is it like that?
Lastly, if Ajax herself gets hypnotized or stuck in some sort of mental power (like that one Bluebird has, despite you two being on the same team), can she escape? You decide. I don't think this power is insanely overpowered so it doesn't really need that many changes, if any.