Ways to delete a file starting with a dash / hyphen:

rm -- -file

The option -- means the end of options for the command.

Another option is to indicate where is the file:

rm ./-file

. is current directory , path to -file is ./-file

Using find:

find . -type f -exec rm {} \;

Finding the inode:

ls -li

Then using find and the inode it can be removed with:

find . -type f -inum <inum> -delete