The only similarities are that V smiles and kills people. Other than that, they have nothing in common. V is a man of profound morality. Joker is a sociopath. They are complete opposites.

noway , are you kidding me
V is wayyyyy better

I don't see it. They're similar in the sense that they wanted their people to do something about the anarchy — the situation — but V didn't set out to kill thousands en masse, just those who made him that way and Valerie. I agree @rory2011; V is a more civilized human being than the Dark Knight's Joker will ever hope to be.

I have absolutely no idea how they could be similar in any way except for the murdering people part.

Knives...they both prefer knives to kill people with. Also, no one knows who they really are. Lastly, they go under false names, But,in many ways, they are very different.