I want to find the fastest way for a wizard to kill an experienced knight. The knight has only been trained to fight against wizards, but has fought many other people and won. The knight has plated armor, a sword, a dagger, and a mace. What do you think is the fastest way for the wizard to make the kill without being killed? The wizard uses the Magic System in the question If many armies containing Wizards Battled each Other, What Would the Outcome Probably be? (the battle is in a small room with many books on wooden shelves and an axe with a wooden handle leaning against the wall. There are a few pebbles lodged in the knight's armor. HINT HINT...) If you want more, give me how the knight would kill the wizard.
I would go about this two ways:
Attack the body head on by causing the knight to have a heart attack or stroke, alternative breaking his neck or skull with a spell
Use teleportation to put something inside the knight's body. Teleport a pebble into his brain or heart, instantly killing him. If you want to be really clever teleport an air bubble into his heart or veins,causing an embolism
Go for the armor
If the knight's armor has a gorget (protects the neck) use it to strangle them. Otherwise manipulate the helmet. Either crush it or give it a quick forceful spin. Crushing it will cause the knight at the very least reel, but hopefully it will crush the skull and thus kill the knight. A forceful spin would cause a number of different results all bad for the knight. The straps holding the helmet in place could strangle or snap. If they snap then the helmet would be on the wrong way blinding the knight. If the helmet is well fitted then the head would get jerked with the helmet possibly breaking the spinal column causing death.
Needless to say the wizard can turn the knight's own armor into a death trap.
Ehhh. I don't like these question as they show the limitations to OP's thinking.
The bones. Wizard can control the bones. Just move his skull and brake his neck.
Bam! Case closed. NEXT!
If your system by "can't control humans" means "can't control anything inside bag made of skin called human" then watch Avatar and learn the way of earthbending. Just move rocks from under the knight and put them on him while he's on the ground.
Accelerate a scrap of something in the room to Mach 6 and smash the knight in the face. A rifle round to the face (which is what this is) will end most threats before the blood splatter hits the back of the victim's helmet.
Note, the opening question didn't ask for stealth. This ain't stealthy.