It’s simply better to do an animation and most likely the solution. Make a simple kick animation with Roblox Animation Editor or whatever animation editor you use and then set the priority to Action.
Copy the id and then create an animation object inside your script with the animation id, reference it with a variable and get the player’s animator through the character. Create a loadanimation and run the play command and now you have a working kick animation
Edit: The reason the tween doesn’t work is probably due to core animations requiring the leg, just use an animation
you can’t cframe your player’s leg because all your bodies are attached together and together attached to HumanoidRootPart with weld or something called attachment. so you can’t cframe your leg off your character.