Final answer:
The weakest part of the needle is the bevel.
Step-by-step explanation:
The part of the needle that is the weakest is the bevel.
The bevel is the slanted, pointed tip of the needle that helps it penetrate the skin or another surface smoothly and easily. It is the most delicate part of the needle and can be easily damaged or blunted.
The other parts of the needle mentioned, such as the shaft, hub, and cartridge penetrating end, are all essential for the needle to function properly, but they are generally stronger and more durable than the bevel.