An assassin with a split personality is hired to protect a client who, unknowingly, his other personality has been hired to kill.

Brilliant - Just thinking about making that play out well makes my head ache, but this is a brilliant hook!

Very good logline. Congratulations!

An instantly interesting logline with a lot of potential!

I'm interested to know more about the client- what are his/her reasons for being the target of the hit and why does he/she choose the protagonist to help protect them.

Agree with the above- what is the trigger for his changing of personalities? Is it in the call to adventure of the mid point reversal that we are introduced to the direct conflict between the personalities?

Consider me intrigued!