Plot hole: Clark is possessed by Dawn. Jonathan shows up and he has a chunk of kryptonite. Jonathan hides the kryptonite behind his back and Clark's body does not feel it until Jonathan takes the kryptonite out from behind his back. What, is Jonathon made of lead or something?
Plot hole: When Dawn enters Clark's body, she slaps Chloe in the face with the back of the hand, and Chloe goes flying. A few minutes later, we see Chloe get up and say that she's fine. Getting backhanded by Clark would make you very far from fine. First of all, Clark can knock someone out just by tapping them on the forehead, as seen in a previous episode. Second, Dawn has no idea of Clark's powers, so she would have used way more force than she actually needed to. The amount of force inflicted from the attack should have caused fatal injuries to Chloe. There's not even a cut or bruise or anything.