Except V is not a "blank slate", no matter how you want to word it. There are personality traits and histories which are constant depending on your lifepath.There is no ultimate truth, cause everyone will play their V the way they imagine the character to be. Especially cause V is a blank slate with a minimal backstory.
Hero, villain, anti-hero, psycho - it's all on the table and only limited by the paths the game offers in the main story, which is already narrow enough.