Sicilian variations ranked by aggressiveness.

1. e4 c5 2. Qh5!! is the uncontested champion of the agressive Sicilian!!

Didn't exactly mean from whites side, 

For black that should be 2...Qa5!!

Svechnikov and Cobra variations are very agressive.

Possibly helpful:

Starting Out: The Sicilian, 2nd Edition by John Emms (2009)

https://web.archive.org/web/20140627122350/http://www.chesscafe.com/text/hansen123.pdf

To my eyes:

Kan (2...e6, 4...a6) maintains total flexibility, but as yet puts no pressure on the centre, so White can develop as he pleases. So it doesn't appear initially aggressive, but play down the main line and Black can aggressively attack the central pawn and pieces with Q etc, if White plays the common Bc4.

https://www.365chess.com/opening.php?ms=e4.c5.Nf3.e6.d4.cxd4.Nxd4.a6.Bc4.Nf6.Nc3.Qc7

Is this why Bc3 is generally recommended? I'm never sure where to put that bishop!

So the answer to the OP is probably "it depends", I guess...

Kan:

LoL Let's say, by definition, that the k-agressiveness of a position is measured by the number of checks in k moves that U can make.  Example (Wayward Queen Attack):

The 1-agressiveness of this position for white is equal to 2 cuz U can make 2 checks:  3. Qxe5+ and 3. Qxf7+.

But you can make aggressive moves that aren't checks, e.g., threaten a pawn. Can you have one scale of aggressiveness? 

P.S. None of that Frenchified spelling please, it's "aggressive" with 2gs. Check out:

https://en.oxforddictionaries.com/spelling/common-misspellings

I second the Kan for its flexibility. It's not aggressive per se, but it can be utilized by an aggressive or sharp player very well. The Sveshnikov, as mentioned, is probably the single most aggressive Sicilian line, though very theoretical and very, very sharp. One wrong move in the first dozen or so could easily lead to disaster.

My notion of k-aggressiveness might be useful for evaluations of 3-check chess games.

P.S. Thanks for correcting my misspelling.

 2. Bb5, Bowdler attack 2. Bc4, 2. Qf3, Amazon attack 2. Qh4 and 2. Qh5 are the most aggressive white's moves of 1-aggressiveness = 1.

It should be measured in pints of beer. Or in your case shots of Ouzo.

What is White's most aggressive line, after the obvious response defuses the Bishop's aggression? Then, what about (off database...) Nh3 aiming for 1-aggressiveness via Ng5?  

Mal_Smith: All that is great for 3-check chess variant. U can try it in Live Chess here.

White is already setting up nasty threats in that position. If black blindly develops with Nc6 he has to meat Qxf7 Kxf7 then Bxe6 check and the king is on f7 with only one health left. Nf3 forces the king to retreat back to e8. Possible, Nh3 is the best move after Nc6.

Grams per cubic centimeter!

Had to look that up: