If you want to delete an entire block of whitespace at point, you can use hungry deletion. This deletes all the contiguous whitespace either before point or after point in a single operation. Whitespace here includes tabs and newlines, but not comments or preprocessor commands.

C-c C-DEL, C-c DEL

Delete the entire block of whitespace preceding point (c-hungry-delete-backwards).

C-c C-d, C-c C-Delete, C-c Delete

Delete the entire block of whitespace after point (c-hungry-delete-forward).

As an alternative to the above commands, you can enable hungry delete mode. When this feature is enabled (indicated by h after a / in the mode line after the mode name), a single =DEL= deletes all preceding whitespace, not just one space, and a single C-d (but not plain =Delete=) deletes all following whitespace.

M-x c-toggle-hungry-state

Toggle the hungry-delete feature (c-toggle-hungry-state). With a prefix argument, this command turns the hungry-delete feature on if the argument is positive, and off if it is negative.

The variable c-hungry-delete-key controls whether the hungry-delete feature is enabled.