Two spaces, or two characters? (2x does the latter.)
:[range]s/^ //
deletes two blanks at the beginning of each line; use % (equivalent to 1,$) as [range] do to this for the entire file.
:[range]s/^..//
deletes the first two characters of each line, whatever they are. (Note that it deletes two characters, not necessarily two columns; a tab character counts as one character).
If what you're really doing is changing indentation, you can use the < command to decrease it, or the > command to increase it. Set shiftwidth to control how far it shifts, e.g.
Do column editing on the block to delete using Ctrl+V (often mapped to Ctrl+Q).
Record a macro on the first row using q1 (or any other number/letter you want to denote the recording register), then replay that macro multiple times using @1 (to use my previous example. Even better, use a preceding number to tell it how many times to run - 10@1 to run that macro 10 times, for example. It does, however, depends on what you recorded - make sure to rewind the cursor 0 or drop one line j, if that's relevant.