You can use :
docker rm -f CONTAINER_ID
It will remove the container even if it is still running.
https://docs.docker.com/engine/reference/commandline/rm/
You can also run your containers with --rm option (e.g. docker run --rm -it alpine), it will be automatically removed when stopped.
https://docs.docker.com/engine/reference/run/#clean-up—rm
Edit: The rm -f might be dangerous for your data and is best suited for test or development containers. @Bernard’s comment on this subject is worth reading.